If an inventory is not already in place, a good start could be to review purchase orders to create an initial inventory. Next, one should conduct an inspection of all areas noting any additional chemicals present that should supplement the initial inventory. It would be ideal to note the location and quantity of each chemical found. Chemical inventories are often maintained as computer files for ease and efficiency in keeping them current. With knowledge of the chemicals in your possession, hazard determinations can now be performed for chemicals in the inventory.

DATA COLLECTION
What data should be collected?

Where can I find the data?

The second step in the hazard determination process is data collection. There are two main questions to be answered: 1) what type of data should be searched for and collected; and 2) how do I go about finding sources that might contain the desired data? You should recognize that the hazard determination process involves the identification of all of the hazards associated with a chemical, not just some of them. This process must be completed even though some data elements may be difficult to locate. Any hazard that exists for the chemical must be identified and communicated to downstream employers and employees.
To complete the hazard identification, information is needed in three categories:

chemical identity; chemical and physical properties; and health effects.

There are numerous sources that could be searched for this information.  A first step is to consult For practical reasons, one should first go to the primary sources (of information such as Wexler's Encyclopedia of Toxicology)those listed in Appendix B.  Theose sources have already compiled data pertaining to many chemicals and are considered generally reliable.  If that search fails to provide the needed data for your chemicals, you may need to search the secondary or computerized literature sources or computerized literature sources.  A number of these additional sourcesthat are also listed in Appendix B.  For new or less commonly -used chemicals, there may not be much data available in any of these sources.  In suchome cases, especially if a new chemical is formed, your company may have to sponsor testing to determine the potential for physical or health hazards, since it may no longer be assumed that the new chemical has the same intrinsic hazards as its components. Such situations are beyond the scope of this documentyou may choose to test the chemical to determine chemical and physical properties and identify hazards.

 In the sections that follow, a discussion of data needs for the three categories of information is provided.  Also, a few recommended key references for the various types of data are listed.  You should recognize that complete and reliable data must be entered on MSDSs and labels in order to meet HCS requirements.  Before the search for hazard data can begin, however, you must identify the exact chemical composition of the chemical(s) or products manufactured or imported.  For mixtures or products, this chemical search includes the name of each chemical in the mixture, including active ingredients, inactive ingredients, and impurities. 

The specific chemical identity of all chemicals on your Chemical Inventory should be carefully and completely compiled.  The specific chemical identity should include:

the chemical name along with common name and synonyms; the Chemical Abstracts Services (CAS) Registry Number (if available); and any other information that reveals the precise chemical designation and composition of the substance.

Correct identification of chemicals is critical for data retrieval. Use the precise chemical name and CAS number when searching for information

An example of the type of chemical identification data needed is presented for Perclene®, a widely used industrial solvent.  Perclean® is a trade name for perchloroethylene or Perc (common name), or more specifically tetrachloroethylene (the actual chemical name (CAS id="_x0000_s1071" Number 127-18-4).  To avoid confusion, literature is often indexed using the CAS number or the primary chemical name.  Thus, the most effective search of computerized databases is conducted using tetrachloroethylene and/or CAS NNumber 127-18-4.  Several databases exist that can be searched for the CAS number or chemical name if one only has a trade or common name.  Another problem with the use of common names is that they may be used for more than one substancemolecular entity.  TCE is sometimes used as an acronym for tetrachloroethylene, although it more frequently refers to trichloroethylene.  Therefore use of the exact chemical name or CAS number would avoids confusion and erroneous data retrieval.  The CAS number is unique for each chemical and should be used, along with the chemical name, when searching computerized databases for information on a specific chemical.

The percent composition should be available in-house for all chemicals and products manufactured or, imported, or used in your business.  The chemical composition information should be based on an analysis of the final or technical product.  A technical grade product is not usually a pure substance and often contains other chemicals such as stabilizers, solvents, carriers, "inert" ingredients, or impurities. For the hazard evaluation process, these other chemicals must also be examinedlisted if they are more than 1.0% of the composition for non-carcinogenic substances or 0.1% of the product if the substance is a carcinogen.

Thus, the initial step is to collect as much data as possible pertaining to the physical and chemical properties and toxicity data for chemicals on your Chemical iInventory.

Key sources of information related to chemical identification are:

Company Records; MSDSs and product safety bulletins from manufacturers or suppliers; OSHA Chemical Information Manual/Database; The Merck Index; ChemID; and Trade Associations.

Physical and Chemical Properties

A chemical may possess more than one physical or health hazard.

The physical properties of a substance can be directly related, in many cases, to the probability of the substance representing a physical hazard.  However, the fact that a substance has a certain physical property can not necessarily be used to necessarily predict a physical hazard.  For example, all volatile substances are not necessarily explosive.  Some solids can also be explosive, (e.g., TNT or grain dust particles).  Nevertheless, knowing the physical properties does have great value in predicting whether a substance may be a physical hazard. 

Key sources of information related to physical and chemical properties include:

NFPA Fire Protection Guide to Hazardous Materials; Department of Transportation 2000 Emergency Response Guidebook; Hazardous Substances Data Bank (HSDB); PMSDSs and product safety bulletins from manufacturers or suppliers; The Merck Index; NIOSH Pocket Guide to Chemical Hazards; CRC Handbook of Chemistry and Physics; Bretherick's Handbook of Reactive Chemicals Hazards; and Trade Associations.

  Health Effects

All potential health hazards must be determined - not just those identified by OSHA

The HCS includes ahas list ofed 14 potential health hazards, as well asas defined the criteria for determining when a chemical represents a health hazard (see Section 3).  In many cases, a chemical may pose more than one type of health hazard.  If your cCompany is manufacturesing a new chemical you may be required tothey must submit premanufacture health effects data to the EPA to comply with the Toxic Substances Control Act (TSCA).  Data submitted by other companies may be available from the EPA.  Thisose assessment and supporting data should also be available in your Company's Hazard Communication Program, as this information is used forused to assist with hazard determination and the preparation of MSDSs and labels.  Data submitted to EPA by other companies may be available to you by contacting the EPA.  For chemicals that have not been studied in-house or via company-sponsored contract toxicology studies, the company should seek toxicity data from the literature, government, or private sources.  Some recommended reference sources are listed below.

Company-sponsored research; PMSDSs and product safety bulletins from manufacturers,  or suppliers, or Internet sites; Hazardous Substances Data Bank (HSDB); Registry of Toxic Effects of Chemical Substances (RTECS®); NIOSH Pocket Guide to Chemical Hazards; OSHA Chemical Information Manual/Database; IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to man; NTP Annual Report on Carcinogens; ACGIH TLVs and BEIs; Hawley's Condensed Chemical Dictionary, 14th Edition; Sax's Dangerous Properties of Industrial Materials, 10th Edition; Published Literature; and Trade Associations.

DATA ANALYSIS

The third step in the hazard determination process is data analysis. This step is the most demanding in technical expertise. The HCS requires that chemical manufacturers and importers conduct a hazard determination to determine whether physical or health hazards exist. In some cases, especially for physical hazards, a definition in the HCS establishes the criteria to be followed. For example, if a liquid has a flash point below 1000 F, it is by definition a "flammable liquid". This type of procedure is a simple data analysis. You can look up the flash point in a standard reference and accept it at face value. In the event your company is manufacturing or importing a chemical for which there is no information on the flash point, you may choose to determine the flash point by laboratory testing, but testing is not required by the HCS.

As a rule, the HCS attempts to minimize the burden of literature search and review while satisfying the need to provide information required to protect employees who are exposed to hazardous chemicals. For this reason, a suggested approach is to go to the most likely sources first to obtain the needed data, and then proceed to additional sources if necessary.

For health hazards, explicit criteria are provided in the HCS for some health hazards. For example, criteria are given for classifying a chemical as highly toxic or toxic based on acute effects, and for designating a chemical as a carcinogen. For other health hazards, a simple generic requirement is provided for the determination of a specific health hazard. The HCS states that "evidence that is statistically significant and which is based on at least one positive study conducted in accordance with established scientific principles is considered to be sufficient to establish a hazardous effect if the results of the study meet the [HCS] definitions of health hazards."
Let's examine this requirement further. There are three key criteria that must be met, namely "statistically significant", "positive study", and "established scientific principles". Thus, the evaluation of study results requires some knowledge of statistics, commonly accepted scientific test methodology, and the definitions of health hazards.

Statistical significance is a mathematical determination of the confidence in the outcome of a test. The usual criterion for establishing statistical significance is the p-value (probability value). A statistically significant difference in results is generally indicated by p<0.05. By p<0.05, there is less than 5% probability that the toxic effects observed were due to chance and were not caused by the chemical. Another way of looking at it is that there is a 95% probability that the effect is real, i.e., the effect seen was the result of the chemical exposure.
The other major indication of statistical significance is the 95% confidence level for a specific data point. Most reports of toxicity testing will include some information on the confidence in the data. For example, an LD50 with a listed value of 9.5 ? 1.2 indicates that if the same study were to be repeated many times, the LD50 would be expected to be within the range of 8.3 - 10.7 on 95 out of every 100 times.

Most toxicity and epidemiology reports will provide an analysis of the data and conclude whether the results were positive or negative, or will describe the adverse effects observed at specific dose levels. By positive, this means that the exposed humans or animals were more likely to develop toxic effects than the non-exposed population. Normally, the investigator's statistical analysis and conclusions can be accepted.

Hazard evaluation relies on professional judgment, particularly in the area of chronic hazards. The performance-orientation of the HCS does not diminish the duty of the chemical manufacturer, importer or employer to conduct a thorough evaluation, examining all relevant data and producing a scientifically defensible determination.

In the remainder of this section, an overview is presented of the HCS designated hazards and their definitions. In addition, a brief discussion is presented to further explain the specific hazard and procedures that can be used to analyze the data. Because this document can only present a limited discussion of the various hazards, you are encouraged to consult references that go into greater detail (see Appendix B of this document).
 
Physical Hazards

A chemical is a physical hazard if it:

is likely to burn or support fire; may explode or release high pressures that can inflict body injury; or can spontaneously react on its own, or when exposed to water.

    

Fire Hazards

Flashpoint is the primary measure of a liquid chemical's propensity to burn.

Combustible and Flammable Liquids

The ability of a chemical to either burn or support burning is a potentially disastrous physical hazard. The two primary measures of the ease with which a liquid will burn are the flashpoint and auto-ignition temperature. The flashpoint is the lowest temperature at which a liquid will emit sufficient vapors to form an ignitable mixture with air. In contrast, auto-ignition is the characteristic of a material in which it will spontaneously burn without the aid of an ignition source, such as a spark or flame. Many agents will burn when ignited whereas there are only a few that will spontaneously erupt into flames. While no single measure of flammability is sufficient for all purposes, the most commonly found measure in the literature is the flashpoint. For this reason, HCS uses flashpoint in classifying the fire hazard of a chemical.

Flammable liquids and combustible liquids are discussed together since flashpoint is the criteria for classification of both. The only difference between a "flammable" and "combustible" liquid is the relative ease (temperature) with which the substance burns or supports burning. The data analysis and hazard categorization are clear. For a pure chemical compound, the assignment to combustible or flammable liquid categories is quite simple:

if the flashpoint is between 1000F - 2000F (37.8oC - 93.30C), it is a combustible liquid; if the flashpoint is below 100oF (38oC), it is a flammable liquid.

The HCS definition for combustible liquid is "any liquid having a flash point between 100oF (37.8oC) and 200o F (93.3oC), except any mixture having components with flashpoints of 200oF (93.3o C) or higher, the total volume of which makes up 99 percent or more of the total volume of the mixture."
The HCS definition for flammable liquid is "any liquid having a flash point below 100oF (38oC), except any mixture having components with flashpoints of 100oF (38oC) or higher, the total of which make up 99 percent or more of the total volume of the mixture."
You see that HCS has made exceptions for chemical mixtures. A mixture will not be categorized as a combustible liquid so long as less than 1% of the total volume of components have flashpoints between 100o and 200o F. For example, if Chemical A has a flashpoint of 1800 F and represents 0.5% of the mixture and all other chemicals have flashpoints above 2000 F, then the mixture is not considered a combustible liquid. Similarly, a mixture will not be categorized as a flammable liquid if it is composed of at least 99% (by volume) of components with flash points above 100oF (38oC). Many mixtures will contain more than 1% of a flammable liquid and the mixture will have a flash point above 100oF. Where data indicating the flashpoint of a chemical is not available, you may choose to test the chemical to determine the flashpoint.

When a substance flashes, the resulting flame will spread through the vapor from the ignition source to the nearby surface of the liquid. From a practical viewpoint, a flammable liquid is potentially more hazardous than a combustible liquid. A flammable liquid presents a fire hazard if present in an open container near an ignition source in an environment in which the temperature is at or below normal room temperature. Examples of flammable liquids (with flash point temperatures) are: acetone (00F), ethyl ether (-490 F), ethyl alcohol (550 F), and gasoline (-450 F). For a combustible liquid to present a fire hazard it must be above normal room temperature. Examples of combustible liquids are kerosene (1000-1620F) and Stoddard solvent (1020-1100F).

The HCS definition for flammable aerosol is "an aerosol that, when tested by the method described in 16 CFR 1500.45, yields a flame projection exceeding 18 inches at full valve opening, or a flashback (a flame extending back to the valve) at any degree of valve opening."
The analysis as to whether the chemical is a flammable aerosol is more difficult and usually must be based upon laboratory testing of the aerosol as emitted from a pressurized container. In practice, most aerosols are mixtures, usually in air, and are primarily propellant formulations of droplets, particles, gases, and/or vapors. Their flammability is highly dependent on the nature of the propellant formulation. Unless data obtained from a literature search pertains to the exact mixture of ingredients in the product, the data may not be accurate. In the event that you choose to test a chemical product to determine if it is a flammable aerosol, the method described in 16 CFR 1500.45 should be used. A positive test is obtained if a flame is projected at least 18 inches at full valve opening, or if there is a flashback (i.e., a flame extends back to the valve) at any degree of valve opening.

Flammable Gas

The HCS definition for flammable gas is "a gas that, at ambient temperatures and pressures, forms a flammable mixture with air at a concentration of less than thirteen (13) percent by volume; or forms a range of flammable mixtures with air wider than twelve (12) percent by volume."
Thus, a gas can be categorized as flammable if the gas:

burns in air at a concentration of less than 13%; or has a lower flammability limit (LFL) of 13% or more with a concentration range for burning in air greater than 12%.  The range is the difference between the LFL and the upper flammability limit (UFL).

The LFL is the minimal concentration of vapor below which combustion will not occur even in the presence of an external ignition source, whereas the UFL is the maximum vapor concentration above which combustion cannot take place. To understand the concept, that at a certain concentration a gas will burn whereas it will not if the concentration is too low or too high, consider the carburetor of an automobile. The carburetor must be correctly adjusted so that the gasoline/air mixture is not too lean or too rich, or the gasoline/air vapor mixture will not burn in the automobile engine. Gasoline has an LFL of 1.4% and an UFL of 7.6%.
Methane and butane are examples of flammable gases that burn at less than 13% concentration in air. Acetone is an example of a flammable liquid that volatilizes but does not represent a flammable gas. This is true because the LFL is 16% and the UFL is 25%, which is a difference of only 9% (the definition requires a difference of at least 12%). On the other hand, ammonia is categorized as flammable since it has a LFL of 15% and an UFL of 28%, a difference of 13%.

Flammable Solid

The HCS definition of a flammable solid is "a solid, other than a blasting agent or explosive as defined in [29 CFR] 1910.109(a), that is liable to cause fire through friction, absorption of moisture, spon¬taneous chemical change, or retained heat from manufacturing or processing, or which can be ignited readily and when ignited burns so vigorously and persistently as to create a serious hazard. A chemical shall be considered a flammable solid if, when tested by the method described in 16 CFR 1500.44, it ignites and burns with a self¬-sustained flame at a rate greater than one ¬tenth of an inch per second along its major axis.”
The analysis as to whether a solid chemical will burn with such intensity to be classified as a flammable solid usually must be based upon the results of laboratory testing. If you choose to test a chemical to determine if it is a flammable solid, such testing should be conducted by the method described in 16 CFR 1500.44. A flammable solid can be ignited readily and then will burn so vigorously as to create a serious fire hazard. Blasting agents or explosives may be solids that burn but with an intensity so great that they are classified as explosives. An example of a flammable solid that can be ignited by friction is the chemical formulation on the head of matches. Some metal powders (such as magnesium) can react with moisture and burn and are thus classified as flammable solids.

Oxidizer

The HCS classifies a chemical as an oxidizer if it is a "chemical other than a blasting agent or explosive as defined in [29 CFR] 1910.109(a), that initiates or promotes combustion in other materials, thereby causing fire either of itself or through the release of oxygen or other gases."
An oxidizing agent is a chemical or substance that brings about an oxidation reaction. The agent may provide the oxygen to the substance being oxidized (in which case the agent has to be oxygen or contain oxygen), or it may receive electrons being transferred from the substance undergoing oxidation (e.g., chlorine is a good oxidizing agent for electron-transfer purposes, even though it contains no oxygen).

Oxidizing materials can initiate or greatly accelerate the burning of fuels. The most common oxidizer is atmospheric oxygen. Oxygen-containing chemicals (e.g., hydrogen peroxide and nitrous oxide) and halogens (e.g., bromine, chlorine, and fluorine) can also be strong oxidizers. Some chemicals may be oxidizers with such an extremely fast burning potential that they are classified as explosives or blasting agents rather than oxidizers. Often the fact that a chemical possesses oxidizing potential can be obtained from an examination of its chemical structure. For example, oxidizing substances usually include recognizable functional chemical groups, e.g., perchlorate (ClO4-), chlorate (ClO3-), chlorite (ClO2-), hypochlorite (ClO-), peroxide (-O-O-=), nitrate (NO3-), nitrite (NO2-), dichromate (Cr2O7=), persulfate (S2O8=), and permanganate (MnO4¬¬-).
While the potential for oxidizing can often be inferred by chemical structure, absolute certainty can only be properly verified in the laboratory since oxidation involves not only the oxidizing potential of the oxidizer, but also the chemical formulation of the fuel to which it comes in contact. Oxidizers are classified by comparison with the oxidizing properties of a standard test chemical, ammonium persulfate, applied to dry, conditioned sawdust. A solid that promotes combustion of the conditioned sawdust at a greater rate than ammonium persulfate is classified as an oxidizer.

Pyrophoric Hazards

The HCS definition for a pyrophoric chemical is "a chemical that will ignite spontaneously in air at a temperature of 130 F (54.40 C) or below." Fortunately, there are only a few chemicals that have the ability to catch fire without an ignition source when exposed to air. Many of these are elements (e.g., lithium, powdered aluminum, magnesium) or organometallic compounds (such as lithium hydride, diethyl zinc and arsine). Moisture in the air often increases the probability of spontaneous ignition of pyrophoric materials.

Explosive Hazards

Compressed Gas

The HCS definition for Compressed Gas is:

(i)  "a gas or mixture of gases having, in a container, an absolute pressure exceeding 40 psi at 700 F (21.10 C): or (ii)   a gas or mixture of gases having, in a container, an absolute pressure exceeding 104 psi at 1300 F (54.40 C) regardless of the pressure at 700 F (21.10 C); or (iii)   a liquid having a vapor pressure exceeding 40 psi at 1000F (37.80 C) as determined by ASTM D-323-72."

All compressed gases are potentially hazardous since they are under great pressure in a container. Accidental rupture of the container and the rapid release of the pressurized gas can result in injury to persons and damage to objects in the vicinity. Not only can the gas be released with great force, but the force of the release may propel the container for a long distance. In addition to the mechanical hazard from the pressure or propelled container, other hazards may exist from the released gas. The hazard from some compressed gases may be strictly mechanical (e.g., compressed air and nitrogen), others may possess other types of hazards, such as being flammable (e.g., methane and propane) or toxic (e.g., ammonia and chlorine).

Explosive

The HCS definition for explosive is "a chemical that causes a sudden, almost instantaneous release of pressure, gas, and heat when subjected to sudden shock, pres¬sure, or high temperature."
Explosives are unstable materials and are of two types. One type consists of material capable of supersonic reactions (detonation), for example, nitroglycerine and TNT. The other type consists of materials (usually mixtures) that burn rapidly but at a subsonic rate. Examples of this type are gunpowder, rocket propellants, and pyrotechnic mixtures (fireworks). The difference between fire and explosion is the rate at which high temperature gases are produced and the physical containment of the burning gases. When high temperature gases build up extremely fast, there can be such a sudden release of energy from the gases that a shock wave or explosion is created. Confining the build-up of high pressure gases in a drum or vessel, which prevents venting of the gases, may promote an increase in the pressure within the restricted volume until an explosion occurs. Such is the principle behind some munitions, which confine high pressure gases until the pressure exceeds the strength of the casing.

Most explosives have a chemical structure that contains both oxidizing and fuel functional groups. Examples of functional groups contained in explosives are: azides, dizonium, and styphnate. While the presence of such functional groups suggests explosive potential, it is usually necessary to confirm this hazard via experimental studies.

Reactive Hazards

These reactionary materials can cause damage to the human body by release of gases that will burn, explode, or produce high pressure that can inflict injury to a person nearby. In some cases, the reactionary materials may release substances that are considerably more toxic than themselves. HCS has defined three types of reactive hazards: organic peroxides, unstable (reactive) materials, and water-reactive materials.

Organic Peroxide

The HCS definition for organic peroxide is "an organic compound that contains the bivalent -O-O structure and which may be considered a structural derivative of hydrogen peroxide where one or both of the hydrogen atoms has been replaced by an organic radical."
The peroxide functional group (-O-O) is relatively unstable and most organic peroxides will spontaneously decompose at a slow rate. Some organic peroxides, however, are capable of very violent reactions with detonation at environmental temperatures, causing fires and explosions. Several organic peroxides are used in the plastics industry to initiate polymerization and serve as cross-linking agents. Recognizing an organic peroxide is quite simple - the presence of the peroxide group (-O-O) in its chemical structure. However, the characterization of the severity of the hazard is usually based upon fairly extensive laboratory testing. Examples of organic peroxides are benzoyl peroxide and allyl hydroperoxide.

Unstable (Reactive) Material

The HCS definition for an unstable (reactive) material is a "chemical which in the pure state, or as produced or transported, will vigorously polymerize, decompose, condense, or will become self-reactive under conditions of shocks, pressure or temperature."
The main difference between an unstable material and an explosive is the rate of the reaction. While the rate of reaction for unstable materials is less than in the case of explosives, the unstable materials can still present a serious hazard due to the generation of high temperatures and pressures. In some cases, the reaction may be rapid enough to approach explosive potential.

Polymerization is a reaction in which small molecules (usually monomers) react with each other to form larger molecules (polymers). In the chemical process, a large amount of heat may be released. This raises the temperature of the monomer mixture that further accelerates the polymerization process until the reaction runs away or explodes.
Decomposition reactions can occur with many chemicals and mixtures. In this process, complex molecules dissociate to form simpler substances. This process may require input of heat or there may be a release of heat during the chemical reaction. The most hazardous reactions are those in which heat is released. If the reactions take place within a vessel, the high temperature may increase the vessel pressure to the point it ruptures or explodes. Examples of unstable materials are acrylonitrile and butadiene.

Water-Reactive Material

The HCS definition for water-reactive material is a "chemical that reacts with water to release a gas that is either flammable or presents a health hazard."
Many chemicals fall in this category. For example, sodium and potassium, when exposed to water, will react and release hydrogen presenting an explosive hazard. Carbides (e.g., calcium carbide) can generate acetylene, a highly flammable gas, when exposed to water. In other cases, the gases released may be highly toxic as in the case of cyanide that can be released when an inorganic salt containing cyanide (e.g., potassium cyanide) comes in contact with water.

Health Hazards

To define with precision every possible health effect that can occur in the workplace as the result of chemical exposure is an unrealistic goal. There can be a variety of toxic effects on different organs, which may depend upon dose level, frequency, duration, and route of exposure. This does not negate the need for employees to be informed of such effects and be protected from them. The HCS provides a list of the most common health hazards. However, it should be stressed that the list does not include all health hazards.

Some of the health hazard definitions provide for an extremely precise testing procedure (e.g., test species or weight range). This is because those test protocols had been codified in previous government regulations. However, other test methods have been developed and are acceptable for hazard determination. In view of this, Appendix A of the HCS indicates that if there are available scientific data that involve other animal species or test methods, they must also be evaluated to determine their applicability.
Assigning chemicals to discrete health hazard categories is not precise, and several schemes have been proposed. Separation into acute and chronic health hazards is used by the American National Standards Institute (ANSI) in its labeling standard (ANSI Z129.1). The main difference between acute and chronic is related to duration of exposure and to the rapidity of onset after exposure.

In some exposure situations, the effects may occur rapidly after a single or short-term exposure (acute effects); in other cases, the damage may accumulate after multiple exposures or over a long exposure period, or arise long after earlier exposures (chronic effects). Examples of chronic effects are cancer and cirrhosis of the liver. A chemical may have the ability to cause both acute and chronic effects. For example, ethyl alcohol can cause death when consumed in large amounts at one time, birth defects when consumed for only a few days by a pregnant woman, and cirrhosis of the liver if consumed for several years. OSHA has listed a number of health hazards, some general or systemic (whole-body) effects, and others that are specific to certain organs (target organs).

Following is a brief description of the HCS identified health hazards. In many cases, the determination is based on data obtained from standard experiments with laboratory animals. Reliable human data is prefered to animal data. However, in many cases, reliable human data are not available, and animal data must be used. The search strategy previously discussed should attempt to obtain human data, animal data, and cell and tissue studies, as well as data on the mechanisms by which a chemical causes toxicity.

Systemic Effects

Carcinogen

Under the HCS, “a chemical is considered to be a carcinogen if:

(a)   It has been evaluated by the International Agency for Research on Cancer (IARC), and found to be a carcinogen or potential carcinogen; or (b)   It is listed as a carcinogen or potential carcinogen in the Annual Report on Carcinogens published by the National Toxicology Program (NTP) (latest edition); or, (c)   It is regulated by OSHA as a carcinogen."

Probable human carcinogens have been listed by OSHA, NTP, and IARC.

OSHA has accepted the prior hazard determination of these expert organizations that have reviewed the human and animal research studies and have concluded that the chemicals listed represent human cancer risks.

As might be expected, there is considerable overlap in these lists as more than one of the scientific organizations may have come to the same conclusion regarding cancer potential. Some examples of workplace carcinogens are asbestos, benzene, lead chromate, beryllium and vinyl chloride.

The simple definition of a carcinogen is "a substance that has the potential to cause cancer." The terminology used to describe cancer may be confusing. Cancer is a type of tumor. A tumor (also known as a neoplasm) is simply an uncontrolled growth of cells. Tumors may be benign or malignant. Benign tumors grow only at the site of origin, and do not invade adjacent tissues or go to distant sites in the body (known as "metastasis"). Except for those that develop deep in vital organs (such as the brain), benign tumors can be successfully treated (usually by surgical removal) and the potential for causing death is low. Malignant tumors are cancers and can grow outside their original site in an organ, invade surrounding tissue, or metastasize to distant organs where they can start new growths of the cancerous tissue. Malignant tumors (cancer) are difficult to treat and frequently cause death of the patient.

Cancers vary greatly in type and behavior in the body. Some cancers grow slowly and rarely metastasize. Others are highly invasive and metastasize rapidly. Cancers are usually named for the specific cell type or organ of origination. For example, squamous cell carcinoma of the lung is a cancer that arose from a squamous cell in the lung. A hepatocellular carcinoma is a cancer arising from a liver cell (hepatocyte). Sometimes the name given to a cancer also reflects its nature. For example, chronic lymphocytic leukemia is a cancer involving lymphocytes (a type of blood cell) which the leukemia is chronic or long-lasting in nature. OSHA, NTP, and IARC report the specific types of cancer caused by chemicals that they list.

How does IARC, NTP, and OSHA classify a substance as a "Carcinogen"?

The operational criteria for labeling or designating a substance as a "carcinogen", as used by the IARC, NTP, and OSHA, relate strictly to the substance's potential for causing cancer in humans. The finding that a substance produced cancer in an experimental animal study does not necessarily result in IARC, NTP, or OSHA designating the substance as a "human carcinogen." These organizations use a "weight of evidence" analysis which includes review of data from animal studies, human epidemiological evidence, and data from cell and tissue studies.

In some cases the collective evidence is substantial and the substance is designated as a "known human carcinogen." In other cases the evidence for human carcinogenicity is not as strong and the substance warrants designation only as a "potential" or "possible" human carcinogen. In the HCS definition of "carcinogen", the terms "carcinogen" and "potential carcinogen" are used. "Carcinogen" in HCS terms relates to the IARC category "Group I - The Agent is Carcinogenic to Humans, and the NTP category for "Substances …Known to be Carcinogenic."

"Potential carcinogens" in HCS terms relates to the IARC category "Group 2A - The Agent is Probably Carcinogenic to Humans", and to the NTP category for "Substances …Which May Reasonably be Anticipated to be Carcinogens."
IARC has a third classification of concern to OSHA. This is Group 2B - "The Agent is Possibly Carcinogenic to Humans." This classification does not rise to the level of concern for Group 2A and therefore those substances are not designated as OSHA carcinogens and the labels for those substances do not require labeling as a carcinogen. However, the fact that IARC has placed a substance into Category 2B should be included on material safety data sheets.

Reports in the periodic literature (e.g., journals) or laboratory reports (e.g., NTP bioassay reports) may indicate positive results from cancer studies of chemicals not listed by OSHA, NTP, or IARC as carcinogens. Some literature reports lack information on experimental design, age of individual animals when tumors were found, purity of chemical tested, etc., making scientific analysis difficult and uncertain. For this reason, a "weight of evidence" approach is used to evaluate the strength of evidence pertaining to human carcinogenicity. The recommended approach is not to discard such information but to collect and make it a part of the information profile for the substance. The results of such studies should be listed on the MSDS. However, the positive results are not sufficient to designate the substance as a carcinogen (and to label it as such). The carcinogen designation is reserved for those substances that have been so designated by IARC, NTP, or OSHA.

Toxic Agents

The HCS classifies chemical agents as toxic or highly toxic based on the number of deaths that occur following brief (acute) exposure of rodents. The difference in the two categories is strictly the dose at which the toxicity (death) occurs. Exposure is by the three major workplace exposure routes, mouth (oral), skin (dermal), or breathing (inhalation). The analysis is based on the LD50 (median lethal dose by oral or dermal exposure) and LC50 (median lethal inhalation concentration for a one-hour exposure. The LD50 and LC50 represent the dose or concentration, respectively, at which 50% of the test animals (and supposedly humans) will be expected to die.

Under the HCS, a highly toxic chemical is "a chemical falling within any of the following categories:

(a)  A chemical that has a median lethal dose (LD50) of 50 milligrams or less per kilogram of body weight [units listed as mg/kg] when administered orally to albino rats weighing between 200 and 300 grams each. (b)   A chemical with a median lethal dose (LD50) of 200 milligrams or less per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between two and three kilograms each. (c)   A chemical that has a median lethal concentration (LC50) in air of 200 parts per million (units listed as ppm) by volume or less of gas or vapor, or 2 milligrams per liter [units listed as mg/l] or less of mist, fume, or dust, when administered by continuous inhalation for one hour (or less if death occurs within one hour) to albino rats weighing between 200 and 300 grams each."

Under the HCS, a toxic chemical is The HCS definition for Toxic is "a chemical falling within any of the following categories:

(a)   A chemical that has a median lethal dose (LD50) of more than 50 milligrams per kilogram but not more than 500 milligrams per kilogram of body weight when administered orally to albino rats weighing between 200 and 300 grams each. (b)   A chemical that has a median lethal dose (LD50) of more than 200 milligrams per kilogram but not more than 1,000 milligrams per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between two and three kilograms each. (c)   A chemical that has a median lethal concentration (LC50) in air of more than 200 parts per million but not more than 2,000 parts per million by volume of gas or vapor, or more than two milligrams per liter but not more than 20 milligrams per liter of mist, fume, or dust, when administered by continuous inhalation for one hour (or less if death occurs within 1 hour) to albino rats weighing between 200 and 300 grams each."

The following table illustrates how a chemical can be classified as a Highly Toxic or Toxic depending on the results of the appropriate animal tests.

Animal Test	Highly Toxic	Toxic
Oral LD50	£ 50 mg/kg	50-500 mg/kg
Dermal LD50	£ 200 mg/kg	200-1000 mg/kg
Inhalation LC50 - gases, vapors	£ 200 ppm	200-2000 ppm
Inhalation LC50 - mists, fumes or dust	2 mg/L	2-20 mg/L

Remember the HCS instructions pertaining to whether a study is scientifically acceptable for hazard determination. While only one positive study is required, it must be:

conducted in accordance with established scientific principles; and the results must be statistically significant.

As can be seen, the acute toxicity for a toxic agent is considerably less than with the highly toxic agents. For example, the break point for oral exposures is 50 mg/kg. Below 50 mg/kg, the chemical is highly toxic whereas if the LD50 is above 50 mg/kg, it is only toxic. Examples of highly toxic chemicals are parathion (with an oral rat LD50 of 2 mg/kg and a dermal LD50 of 22 mg/kg) and methyl isocyanate (with an inhalation one-hour LC50 in rats of 45 ppm). Examples of toxic chemicals are chloroform (with an LD50 of 140 mg/kg), acrylonitrile (with an 24-hour dermal LD50 between 200 and 2000 mg/kg), and ammonia (with an inhalation one-hour LC50 in rats between 200 ppm and 2000 ppm). Agents having an oral LD50 greater than 500 mg/kg are not classified as toxic. This does not mean that they do not represent a health hazard (e.g., the chemical could present a chronic hazard, such as cancer or hepatotoxicity), but only that they are not classified as toxic under the HCS.

While these criteria are based on laboratory animals that are quite different than humans, the relative response between animals and humans is generally comparable on a per body weight basis. Thus, expressing the effect in terms of kilogram of body weight provides a satisfactory basis for determining potential human effects based on animal research results. Translating a 50 mg/kg LD50 to an understandable situation in humans, if a group of 150-pound humans ingested about one-half teaspoon of such a chemical, approximately 50% would be expected to die.
The HCS provides criteria for classifying chemicals as highly toxic and toxic based on experiments that used 200-300 gram albino rats or 2-3 kilogram albino rabbits. However, current testing procedures accept other species and do not prescribe exact weights. Although specific criteria are provided, the HCS also indicates that information pertaining to other species and test methods is also relevant. In determining hazards, you need to search for and analyze all data pertaining to toxicity and make judgments as to whether the tests were conducted using appropriate and accepted methodology. If the studies are acceptable, the data should be used as appropriate to determine whether the chemical is highly toxic, toxic, or belongs to another health hazard category (e.g., hepatotoxicity or irritant).

Irritant

Irritant - reversible inflammatory reaction

Under the HCS, an irritant is "A chemical, which is not corrosive, but which causes a reversible inflammatory effect on living tissue by chemical action at the site of contact. A chemical is a skin irritant if, when tested on the intact skin of albino rabbits by the methods of 16 CFR 1500.41 for four hours exposure or by other appropriate techniques, it results in an empirical score of five or more. A chemical is an eye irritant if so determined under the procedure listed in 16 CFR 1500.42 or other appropriate techniques."

The difference between an irritant and a corrosive is the ability of the body to repair the tissue reaction. With irritants the inflammatory reaction can be reversed whereas with corrosive damage it is permanent or irreparable. The site of irritation is often the skin or eye but can also be any mucous membrane or other tissue that the chemical comes in contact with. This could include the mouth or throat if the irritant is swallowed, and the nose or lungs if the irritant is inhaled. If an immunologic mechanism (allergy) is responsible for the tissue reaction, the material will be classified as a sensitizer rather than an irritant. Examples of irritants are acetic acid, ammonia, and isopropyl alcohol. The standard toxicology test for inflammation consists of the application of a substance to the shaved skin of white rabbits. White rabbits have been widely used as the irritation is easy to detect and the results have been shown to be highly predictive of potential skin effects in humans. Data obtained with other strains or species can also be used in the determination of irritation potential.

Corrosive

Corrosion - irreversible tissue injury

The HCS definition for corrosive is "A chemical that causes visible destruction of, or irreversible alterations in, living tissue by chemical action at the site of contact. For example, a chemical is considered to be corrosive if, when tested on the intact skin of albino rabbits by the method described by the U.S. Department of Transportation in appendix A to 49 CFR part 173, it destroys or changes irreversibly the structure of the tissue at the site of contact following an exposure period of four hours. This term shall not refer to action on inanimate surfaces.”

Corrosion is manifested by ulcers, cell death, and scar formation. The site of a corrosive effect can be any place on the body that the chemical contacts. This is often the skin or eye but can also be any mucous membrane (such as the mouth or esophagus if swallowed and the nose and trachea if inhaled).

Generally speaking, corrosive materials have a very low pH (acids) or a very high pH (bases). Strong bases are usually more corrosive than acids. Examples of corrosive materials are sodium hydroxide (lye) and sulfuric acid.

The standard toxicology test for corrosivity uses white rabbits with the material applied to the shaved (but not damaged) skin. Experience has shown that results obtained with white rabbits are highly predictive of potential skin effects in humans. Corrosion determined using other species and procedures must also be considered in the decision as to classification as a corrosive.

Sensitizer

Sensitizer - produces hyperallergic condition

The HCS definition for sensitizer is "A chemical that causes a substantial proportion of exposed people or animals to develop an allergic reaction in normal tissue after repeated exposure to the chemical."

A sensitizer (allergen) causes little or no reaction in man or test animals on first exposure. The problem arises on subsequent exposures when a marked immunological response occurs. The response is not necessarily limited to the contact site as it may be a generalized body condition. Skin sensitization is common in industry. Respiratory sensitization and generalized hyperallergy to a few chemicals has also been known to occur. Well-known examples of sensitizers are toluene diisocyanate, nickel compounds, and poison ivy.

Target Organ Effects

Hepatotoxin

Hepatotoxin - liver toxin

The HCS definition for hepatotoxins is “chemicals which produce liver damage”. Signs of hepatotoxicity may include jaundice and liver enlargement. Hepatotoxicity includes not only the liver but also the gall bladder and bile duct. The liver is particularly susceptible to foreign chemicals because of its large blood supply and the major role it plays in metabolism. These factors can result in exposure to high doses of a toxicant and the production and immediate exposure to potentially toxic metabolites.
The primary forms of hepatotoxicity are: chemical hepatitis (inflammation of the liver), fatty liver or steatosis (lipid accumulation in hepatocytes), hepatic necrosis (death of the hepatocytes), cholestasis (stoppage of bile flow and backup of bile salts in the liver), cirrhosis (chronic fibrosis, often due to alcohol), hypersensitivity (immune reaction resulting in hepatic necrosis) and hepatic cancer (cancer of the liver). Examples of hepatotoxins are arsenic, carbon tetrachloride, ethyl alcohol, halothane, and vinyl chloride.

Nephrotoxin

Nephrotoxin - kidney toxin

The HCS definition for nephrotoxins is “chemicals which produce kidney damage”. Signs often include edema and proteinuria. The kidney is highly susceptible to toxicants for two reasons. There is a very high volume of blood flow through the kidney, and the kidney can filter large amounts of toxins that can concentrate in the kidney tubules. The kidney eliminates body wastes, maintains body levels of electrolytes and fluids, and produces special enzymes and hormones that regulate blood pressure, pH, calcium, and the production of red blood cells. Thus, the effects of nephrotoxicity are systemic in nature, such as hypertension, body fluid and electrolyte imbalance, and anemia. The primary forms of nephrotoxicity are nephritis (inflammation of the kidneys), glomerulonephritis (damage to the glomerulus portion of the nephron), and acute or chronic renal failure.

Examples of nephrotoxins are heavy metals (e.g., chromium, lead, mercury, and uranium) and halogenated hydrocarbons (e.g., carbon tetrachloride and chloroform). While some toxins cause acute effects, many exert their toxicity by long-term exposure at lower levels.

Neurotoxins

Neurotoxin - nervous system toxin

The HCS definition for neurotoxins is "chemicals which produce their primary toxic effects on the nervous system." The nervous system directs many of the body's activities so that changes in the nervous system may be apparent throughout the body. Electrical impulses move through the body via neurons (nerve fibers). Toxins can damage cells of the central nervous system (brain and spinal cord) or the peripheral nervous system (nerves outside the central nervous system).

The primary types of neurotoxicity are: neuronopathies (neuron injury), axonopathies (axon injury), demyelination (loss of axon insulation), and interference with neurotransmission. Signs and symptoms of neurotoxicity include narcoses, behavioral changes, and decreases in motor function. Examples of neurotoxins are carbon disulfide, ethylene oxide, hexane, lead, and mercury.

Blood/Hematopoietic Toxin

Hemotoxin - toxicity to bone marrow or circulating blood cells

Blood/hematopoietic toxins are also referred to as hemotoxins or hematotoxins. The HCS defines these chemicals as "Agents which act on the blood or hemato-poietic system: Decrease hemoglobin function; deprive the body tissues of oxygen."

While one might consider the blood and hematopoietic system as independent tissues, they are intimately related. The hematopoietic system gives rise to the blood elements (cells and platelets). Toxins can act at various points in the hematopoietic/blood system. Some affect the circulating blood elements interfering with their function. Others damage the hematopoietic system and may prevent it from producing the blood elements.

The formed elements (cells and platelets) in the circulating blood are usually not directly affected by toxins. An exception are the red blood cells (erythrocytes). Several toxic agents can bind with the hemoglobin of the red blood cells and interfere with transport of oxygen to body tissues (hypoxia). Examples of chemicals that bind with hemoglobin and cause hypoxia, by interfering with oxygen transporting capability of the blood, are carbon monoxide, sodium nitrite, and hydrogen sulfide. Cyanides also cause hypoxia by interfering with the tissue cell's ability to utilize oxygen.

The more common form of hemotoxicity results from chemicals acting directly on the hematopoietic tissues (blood-forming tissue). The primary effect is a decrease in formation of specific blood cells so that the number in the circulating blood is reduced, impairing their ability to function normally. For example, phenothiazine and anticonvulsant drugs can damage the bone marrow cells that give rise to the granuloctyes and decreased ability to fight infections. Aspirin and nitroglycerin can be toxic to megakaryocytes that produce blood platelets. The decrease in platelets impairs blood-clotting capability. Other toxins, e.g., arsenic, benzene, and chlordane can cause a decrease in the formation of all blood elements, a condition known as aplastic anemia. Cancer of the hematopoietic tissues (primarily acute myelogenous leukemia) also occurs due to exposure to some industrial chemicals and drugs, for example, benzene, chloramphenicol, and phenylbutazone.

Respiratory Toxin

Respiratory toxin - affects lung and other areas of respiratory system

The HCS definition for agents which damage the lung is “chemicals which irritate or damage pulmonary tissue.” These are commonly known as respiratory toxins.

The primary function of the respiratory system is to deliver oxygen to the bloodstream and remove carbon dioxide from the blood. Thus, damage to the respiratory tissues interferes with blood/gas exchange that may cause serious malfunction of all tissues of the body, especially the brain and heart. Respiratory toxicity can occur in the upper respiratory system (nose, pharynx, larynx, and trachea) or in the lower respiratory system (bronchi, bronchioles, and lung alveoli). The primary types of respiratory toxicity are pulmonary irritation, asthma/bronchitis, reactive airway disease, emphysema, allergic alveolitis, fibrotic lung disease, pneumoconiosis, and lung cancer. Some exert their toxicity quickly (acute effects, such as pulmonary irritation) while others act over a long period to time (chronic effects, such as pulmonary fibrosis). Examples of respiratory toxins are asbestos, formaldehyde, ozone, nitrogen dioxide, and silica.

Reproductive Toxin

Reproductive toxicity - includes sterility, abortion, birth defects, child mortality and childhood cancer

The HCS definition for reproductive toxins is "chemicals which affect the reproductive capabilities including chromosomal damage (mutations) and effects on fetuses (teratogenesis)." This definition is comprehensive and incorporates toxic effects on all elements of the process of reproduction, including damage to the germ cells (sperm and ova).

Thus, a wide variety of effects can occur, including sterility, decreased libido, impotence, interrupted pregnancy (abortion, fetal death, or premature delivery), birth defects in the offspring, altered sex ratio and multiple births, chromosome abnormalities, childhood morbidity, and childhood cancer. Examples of reproductive toxins are lead and 1,2-Dibromo-3-chloropropane (DBCP). Reproductive toxicity can involve toxicant damage to either the male or female reproductive system. Those substances that can cause birth defects are referred to as teratogens.

The term developmental toxicity refers to adverse effects observed in the embryo, fetus or newborn. In testing, these reproductive effects are usually considered separately from those effects on an adult animal's capacity to successfully mate (fertility) and deliver and nurture offspring (perinatal and postnatal development and maternal function). Developmental toxicity can result from toxicant exposure to either parent before conception or to the mother and her developing embryo-fetus. The three basic types of developmental toxicity are: Embryolethality which is the failure to conceive, spontaneous abortion or stillbirth; embryotoxicity which is the growth retardation or delayed growth of specific organ systems, and teratogenicity which pertains to irreversible conditions that leave permanent birth defects in live offspring (e.g. cleft palate, missing limbs).

Chemicals can cause developmental toxicity by two mechanisms. They can act directly on cells of the embryo causing cell death or cell damage that leads to abnormal organ development. A chemical might also induce a mutation in a parent’s germ cell that is transmitted to the fertilized ovum. Some mutated fertilized ova develop into abnormal embryos.

Genetic toxicity has also been included in the HCS definition of reproductive toxins. Genetic effects result from damage to DNA and altered genetic expression. This process is known as mutagenesis. The genetic change is referred to as a mutation and the agent causing the change as a mutagen. There are three types of genetic change: Gene mutation is a change in DNA sequence within a gene. Chromosome aberrations are changes in the chromosome structure. Aneuploidy/polyploidy is an increase or decrease in number of chromosomes

If the mutation occurs in a germ cell (sperm and ova) the effect can be heritable. There is no effect on the exposed person, rather the effect is passed on to future generations. If the mutation occurs in a somatic cell (all body cells except sperm and ova), it can cause altered cell growth (e.g. cancer) or cell death (e.g. teratogenesis) in the exposed person.

Cutaneous Hazard

Cutaneous hazard - irritation, corrosion, allergy, pigment changes, cancer

The HCS definition for cutaneous hazards is "chemicals which affect the dermal layer of the body." This overlaps to a certain extent with the previously described hazards, irritant and corrosive. However, here we are concerned only with effects of toxins on the skin. A variety of skin conditions can arise from exposure to toxic substances. Contact dermatitis or inflammation of the skin can be of two types, irritant dermatitis and allergic contact dermatitis. The basic inflammatory reaction is the same but the cause and progress of the dermatitis differs. With irritant dermatitis the effect is immediate without prior exposure, whereas the allergic dermatitis requires previous exposure with the development of allergy or sensitization. Contact dermatitis is common in industry and usually consists of redness (erythema), thickening and firmness of skin (induration), flaking (scaling), and blisters (vesiculation). Normally, the contact dermatitis is reversible if the irritant or allergen is removed.

In contrast, chemical burns can sometimes occur in which immediate necrosis, ulceration, and sloughing of the skin occurs. This injury may be permanent and can leave deep wounds that scar or require transplanted skin to repair the damaged area. Some chemicals can cause irritation by defatting of the skin; for example, commonly used ketones or chlorinated compounds, such as the solvents trichloroethylene, methylene chloride, and gasoline.

Cutaneous hazards may cause skin reactions that are neither irritation or allergic reactions. Oils and halogenated aromatic hydrocarbons can cause acne, mercury and lead can cause increased pigmentation of the skin, hydroquinone can cause decreased pigmentation, and beryllium and chromium can stimulate a granulomatous reaction (having the appearance of small, benign tumors). Skin cancer can be induced by workplace exposure to UV light and arsenic.

Eye Hazard

Eye hazard -- from direct chemical contact with conjunctiva or cornea, or from agent that travels through the bloodstream to the optic nerve and retina.

The HCS definition for eye hazards is "chemicals which affect the eye or visual capacity." The primary toxic effects from direct exposure of chemicals to the eye are conjunctivitis or corneal damage. Conjunctivitis is inflammation of the conjunctiva, the delicate membrane that lines the eyelids and covers the eyeballs. The cornea is the transparent front surface of the eyeball.

Chemicals that accidentally splash onto the face can directly contact either of these eye structures. Acids and strong alkalis (such as lye) may cause severe corneal corrosion and may result in permanent blindness. Organic solvents (such as acetone) and detergents can cause temporary clouding of vision, primarily due to dissolving of fats from the cornea.

Some chemicals can cause toxic effects to the eye even if they do not directly contact the eye. Chemicals that are inhaled or ingested may move to the eye through the blood circulation and produce eye damage. 2-4-Dintrophenol (wood preservative) can cause cataracts after ingestion. The ingestion of thallium salts (in pesticides) and methanol (wood alcohol) has been associated with blindness due to damage to the optic nerve. Retina damage has been associated with exposures to arsenicals and carbon disulfide.

While animal ocular tests are routinely conducted during the safety testing of new chemicals, detection of damage to the optic nerve and retina are difficult to detect. Unfortunately, this information results from case reports of humans exposed to toxic substances. Irritation and corrosion may be predicted on the basis of the pH of the chemical substance. However, pH has little value in predicting other types of ocular toxicity.


Other Types of Target Organ Hazards

Industrial chemicals can cause toxicity of the cardiovascular system and immune system.

As previously indicated, the HCS does not identify all possible target organ effects due to exposure to toxic agents. Certain chemicals may target one or more specific organs not listed in the HCS. Based on the chemistry of the toxin and how it is metabolized and distributed in the body, virtually any organ or organ system may be at potential risk. Therefore data found in the literature search pertaining to other organs must also be evaluated and documented. Of the other important health hazards listed in Table 2, effects on the cardiovascular system and immune system are most likely to be reported for industrial chemicals.

Cardiovascular toxicity has been reported for several industrial chemicals. The effects on the heart are primarily interference with cardiac nerve transmissions or damage to the heart musculature (cardiomyopathy). Either type of effect can prevent the heart from contracting (beating) normally so that the blood is not adequately circulated through the body, resulting in multiple organ damage and dysfunction. Some chemicals can also affect the circulatory vessels (veins, arteries and capillaries). Examples of cardiovascular toxins are ethanol and cobalt (cardiomyopathy); arsenic (arteriosclerosis and vascular lesions); toluene and halogenated alkanes (arrhythmias); and mercury (aortic lesions).

Toxicity to the Immune System can lead to several different effects, depending on which cells are damaged, and whether the toxic effects are due to impairment of the immune system (immunosuppression) or the effects are caused by an altered or enhanced immune system (e.g., allergy/hypersensitivity and autoimmunity). A wide variety of industrial chemicals are known to be immunotoxins, including toluene diisocyanate, formaldehyde, silicone, benzene, heavy metals, halogenated aromatic hydrocarbons, and insecticides.

DATA DOCUMENTATION

Document the following: Chemical inventory Procedures used in hazard determination Hazardous chemicals list.

The fourth and final step in the hazard determination process is very important. All the other steps will be wasted if you do not document your findings carefully. If a chemical is found to be hazardous, the findings should be documented in order to assist in preparing labels and MSDSs, and to maintain a record for future reference and updating. In addition, the HCS requires data documentation of the hazard determination as follows:

Chemical manufacturers, importers, or employers evaluating chemicals shall describe in writing the procedures they use to determine the hazards of the chemical they evaluate. The written procedures are to be made available, upon request, to employees, their designated representatives, the Assistant Secretary and the Director [OSHA and NIOSH officials]. The written description may be incorporated into the written hazard communication program required under paragraph (e) of this section [the HCS].

It is recommended that this chemical inventory be computerized for future sorting, additions, deletions, and status reports.

Description of Procedures Used for Hazard Determination

As indicated previously, the procedures used to determine hazards of chemicals are to be written down and made available upon request to employees as well as OSHA and NIOSH officials. This written description of procedures should be incorporated into the company’s written hazard communication program.

The procedures used for the following hazard determination steps should be described in detail:

• Development of chemical inventory;
• Search strategy and sources used to obtain data on chemicals for which hazard determinations are conducted;
• References retrieved and used to identify each specific physical or health hazard;
• Summary for each retrieved reference that contained relevant data (retrieved computer abstracts can be used);
• Summary of important data that was used for hazard determination; and
• Identification of hazards.

FAST - if greater than 3.0. Exam¬ples: Methyl Ethyl Ketone = 3.8, Acetone = 5.6, Hexane = 8.3.

MEDIUM - if 0.8 to 3.0. Exam¬ples: 190 proof (95%) Ethyl Alcohol = 1.4, VM&P Naphtha = 1.4, MIBK = 1.6.

SLOW - if less than 0.8. Exam¬ples: Xylene = 0.6, Isobutyl Alcohol = 0.6, Normal Butyl Alcohol = 0.4, Water = 0.3, Mineral Spirits = 0.1.

(a) Tagliabue Closed Tester (see American Na¬tional Standard Method of Test for Flash Point by Tag Closed Tester, Z11.24 1979 [ASTM D 56-79]).
(b) Pensky-Martens Closed Tester (see American National Standard Method of Test for Flash Point by Pensky-Martens Closed Tester, Z11.7-1979 ASTM D93-79]).
(c) Setaflash Closed Tester (see American Na¬tional Standard Method of Test for Flash Point by Setaflash Closed Tester [ASTM D 3278-78]).