|<< Back to OSHA Technical Manual (OTM) Table of Contents
[Updated 6/24/2008 (08-05 (TED 01))]
||Effective Date: 1/20/1999
Directive Number: TED 01-00-015 [TED 1-0.15A]
OCCUPATIONAL SKIN EXPOSURE
- Basics of Skin Exposure
Risk Assessment (Establishing a Significant Risk of Skin Exposure)
- Biological Monitoring
- Wipe Sampling Methodology
- Enforcement Recommendations
Appendix II: 2-1. General Procedure for Collecting Wipe Samples
APPENDIX II: 2–1. GENERAL PROCEDURE FOR COLLECTING WIPE SAMPLES
The purpose of this chapter is to provide guidance to OSHA Compliance Safety and
Health Officers (CSHOs) and to the industrial hygiene community on the potential
for skin exposure to chemicals in the workplace and the available means of
assessing the extent of skin exposure. Skin exposure to chemicals in the
workplace is a significant problem in the United States (U.S.). Both the number
of cases and the rate of skin diseases in the U.S. exceed recordable respiratory
illnesses. In 2006, 41,400 recordable skin diseases were reported by the Bureau
of Labor Statistics (BLS) at a rate of 4.5 injuries per 10,000 employees,
compared to 17,700 respiratory illnesses with a rate of 1.9 illnesses per 10,000
In addition to causing skin diseases, many chemicals that are readily absorbed
through the skin can cause other health effects and contribute to the dose
absorbed by inhalation of the chemical from the air. Skin absorption can occur
without being noticed by the employee and in some instances may be a more
significant route of exposure than the respiratory system. This is particularly
true for non-volatile chemicals that are hazardous and which remain on work
surfaces for long periods of time. The number of occupational illnesses caused
by skin absorption of chemicals is not known. It is, however, argued that of an
estimated 60,000 deaths and 860,000 occupational illnesses per year in the U.S.
attributed to occupational exposure, even a relatively small percentage caused
by skin exposure would represent a significant health risk.2
- BASICS OF SKIN EXPOSURE
Skin contact with chemicals can result in irritation, allergic response,
chemical burns, and allergic contact dermatitis. Irritant dermatitis may be
caused by a variety of substances such as strong acids and bases. Some examples
of chemicals which are potent irritants include: ammonia, hydrogen chloride, and
sodium hydroxide. Generally, primary irritants produce redness of the skin
shortly after exposure with the extent of damage to the tissue being related to
the relative irritant properties of the chemical. In most instances, the
symptoms of primary irritation are observed shortly after exposure; however,
some chemicals produce a delayed irritant effect because the chemicals are
absorbed through the skin and then undergo decomposition with aqueous portions
of the skin to produce primary irritants. Ethylene oxide, epichlorohydrin,
hydroxylamines, and the chemical mustard agent (bis(2-chloroethylsulfide)) are
classic examples of chemicals which must first decompose in the aqueous layers
of the skin to produce irritation.
Allergic contact dermatitis, unlike primary irritation, is caused by chemicals
which sensitize the skin. This condition is usually caused by repeated exposure
of the skin to a relatively low concentration chemical which ultimately results
in an irritant response. Frequently, the sensitized area of skin is well
defined, providing an indication of the area of the skin which has been in
contact with the sensitizing material.
A wide variety of both organic and inorganic chemicals can produce contact
dermatitis. Some examples of these chemicals include: aromatic nitro compounds
(e.g., 2,4-dinitrochlorobenzene), diphenols (e.g., hydroquinone, resorcinol),
hydrazines and phenylhydrazines, piperazines, acrylates, aldehydes, aliphatic
and aromatic amines, epoxy resins, many other organic chemicals, and metals
(e.g., hexavalent chromium). These substances can also produce contact
sensitization. Allergic contact dermatitis is present in virtually every
industry, including agriculture, chemical manufacturing, rubber industry, wood,
painting, bakeries, pulp and paper mills, and many others.
Lastly, there is a class of chemicals which can produce allergic reactions on
the skin after exposure to sunlight or ultraviolet (UV) light. These chemicals
are called photosensitizers. Polynuclear aromatic compounds from coke ovens and
the petroleum-based tars are examples of chemicals which can be photoactivated
on the skin to cause an irritant response.
A. Skin Absorption
In addition to the effects that chemicals can directly have on the skin, the
skin also acts as a pathway for chemicals to be absorbed into the body. The skin
primarily consists of two layers - the epidermis and the dermis. The outer layer
of the epidermis is composed of a compacted layer of dead epidermal cells called
the stratum corneum which is approximately 10 − 40 micrometers thick. The
stratum corneum is the primary barrier for protection against chemical
penetration into the body. Its chemical composition is approximately 40%
protein, 40% water, and 20% lipid or fat. Because skin cells are constantly
being produced by the body, the stratum corneum is replaced by the body
approximately every two weeks.
Chemical absorption through the stratum corneum occurs by a passive process in
which the chemical diffuses through this dead skin barrier. Estimates of the
amount of chemicals absorbed through the skin as discussed below assume that the
chemicals passively diffuse through this dead skin barrier and are then carried
into the body by the blood flow supplied to the dermis.
A number of conditions can affect the rate at which chemicals penetrate the
skin. Physically damaged skin or skin damaged from chemical irritation or
sensitization will generally absorb chemicals at a much greater rate than intact
skin. Organic solvents which defat the skin and damage the stratum corneum may
also result in an enhanced rate of chemical absorption. If a chemical
breakthrough occurs while wearing gloves or other protective clothing, the
substance becomes trapped against the skin, leading to a much higher rate of
permeability than with uncovered skin. An employee who wears a glove for an
extended period of time experiences enhanced hydration to the skin simply
because of the normal moisture which becomes trapped underneath the glove. Under
these conditions, chemical breakthrough or a pinhole leak in a glove can result
in greater chemical absorption due to increased friction, contact time with the
substance and increased temperature resulting in a higher overall absorption
through the skin. In another example, an employee may remove a glove to perform
a task which requires increased dexterity, exposing the skin to additional
chemical exposure even after redonning the glove.
- RISK ASSESSMENT (ESTABLISHING A SIGNIFICANT RISK OF SKIN EXPOSURE)
The absorption of chemicals through the skin can have a systemic toxic effect on
the body. In many instances dermal exposure is the principal route of exposure,
especially for chemicals which are relatively non-volatile. For example,
biological monitoring results of coke oven workers coupled with air monitoring
of the employees’ exposure demonstrated that 51% of the average total dose of
benzo[a]pyrene absorbed by coke oven workers occurred via skin contact.3 Studies
of employees in the rubber industry suggest that exposure to genotoxic chemicals
present in the workplace is greater via the skin than via the lung.4
For chemicals which are absorbed through the skin and which are hazardous, the
levels of exposure on the skin must be maintained below a level at which no
adverse effects would be observed. One of the simplest ways of determining this
amount is to estimate the amount of a chemical which can be absorbed into the
body based upon an air exposure limit. For example, the OSHA permissible
exposure limit (PEL) for methylenedianiline (MDA) is 0.1 part per million (ppm),
or 0.81 milligrams per cubic meter (mg/m3). If we assume that the average
employee breathes 10 m3 of air a day, and further assume that all of the MDA is
absorbed from the air at the PEL, then the maximum allowable dose to the body
per day becomes:
(0.81 mg/m3)(10 m3) = 8.1 mg maximum allowable dose to the body for MDA
In addition to using OSHA PELs, American Conference of Governmental Industrial
Hygienist (ACGIH) Threshold Limit Values (TLVs) or internal corporate air
concentration values can also be used to establish the maximum allowable dose in
the same manner. This method assumes that the toxic effects of the chemical are
systemic and that the toxicity of the chemical is independent of the route of
The lethal dose to the skin which results in death to 50% of exposed animals
(LD50 dermal) is also a useful comparative means of assessing dermal exposure
hazards. The OSHA definition of a toxic chemical (defined in 29 CFR 1910.1200
App. A) as it relates to skin exposure is a chemical which has a "median lethal
dose (LD50) of more than 200 milligrams per kilogram but not more than 1000
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." If available, the
no observable effect level (NOEL) can also be useful in establishing a safe
exposure level. Skin notations or skin designations for chemicals listed as ACGIH TLVs or the OSHA PELs are also useful guides; however, many chemicals
(e.g., hexone, xylene and perchloroethylene) which can pose a dermal hazard are
A. Estimating the Extent of Absorption of Chemicals through Skin
For exposure to chemicals which are recognized as systemic toxins, that is,
chemicals which are toxic once absorbed into the bloodstream, the route of
exposure to the chemical is not important. Hence, the maximum allowable dose can
be used as a basis for determining if a chemical poses a skin exposure hazard.
The extent of absorption of a chemical through the skin is a function of the
area of the exposed skin, the amount of the chemical, the concentration of the
chemical on the skin, the rate of absorption (flux rate) into the skin, and the
length of time exposed.5 Assume for example, that an employee has contact on the
interior portion of both hands to a solution of phenol (10% solution by weight)
for two hours. Approximately how much phenol would be absorbed? The flux rate,
J, is determined by:
J = (Kp)(Concentration of Chemical on Skin)
Kp for phenol = 0.0043 cm/h (Kp values available from Exhibit B-2 in EPA Dermal
(Kp – skin permeability coefficient)
Thus, at a concentration of 10% by weight (10 g/100 cm3, 10,000 mg/100 cm3, or
J = (0.0043 cm/h)(100 mg/cm3) = 0.43 mg/(cm2•h)(flux rate)
Hence, under these conditions, 0.43 mg of phenol will be absorbed through the
skin per cm2 of exposed skin per hour.
Therefore, the absorbed dose of phenol through the skin of an employee's two
hands (both palms exposed – approximate area: 840 cm2) would be determined by:
Absorbed Dose = (840 cm2)(0.43 mg/( cm2•h)) (2 h) = 722 mg absorbed over a
2-hour period. This compares to an allowable dose (PEL = 19 mg/m3) via the lung
for an 8-hour exposure of (19 mg/m3)(10 m3) = 190 mg. Hence, this 2-hour
exposure via the skin would represent absorption of phenol which is 3.8 times
the allowable dose via the lung.
The following hypothetical example illustrates the relative importance of skin
absorption as a factor in exposure. Let us assume that an employee is wearing
gloves and the gloves are exposed to a phenol solution. Let us further assume
that the penetration through the gloves is detected by a hand wipe sample, and
that 75 mg of phenol is reported present from a water hand rinse of the
employee’s hands taken before lunch. Let us further assume that the amount of
phenol detected inside the glove at the lunch break represents a uniform
constant exposure which occurred shortly after the beginning of the work shift.
Finally, let us further assume that the 75 mg of phenol is present in
approximately 10 milliliter (mL) of water (perspiration) present on the surface
of the skin. How much phenol was absorbed in the 8-hour period?
First, we determine the flux rate: J = (0.0043 cm/h)(75 mg/10 cm3) = 0.0322
mg/(cm2•h) (flux rate)
Absorbed Dose = (840 cm2)(0.0322 mg)/(cm2•h)(8 h) = 216 mg of phenol absorbed
Hence, the estimated amount of phenol absorbed into the body is greater than the
maximum allowable amount of phenol based upon inhalation of 190 mg.
B. Glove Permeability
Penetration of chemicals through gloves is similar to the penetration of
chemicals through the skin. Glove manufacturers publish breakthrough data which
reflect the length of time which occurs before a chemical penetrates through a
particular type of glove material. These tests are performed using ASTM
(American Society for Testing and Materials) Method F 739 in which a pure, or
neat, chemical is placed on one side of a section of the glove material and the
time to penetrate through the glove is measured by analyzing the air on the
other side of the glove to detect chemical breakthrough.
Unfortunately, these breakthrough times can be misleading because actual
breakthrough times will typically be less than reported by the manufacturer.
This is the case because the temperature of skin is greater than the test
temperature, and this results in an increased permeability rate. Secondly, glove
thinning occurs along pressure points where an employee may grip a tool or
otherwise exert pressure on an object while wearing a glove. Glove degradation
and reuse of gloves can also dramatically reduce the effectiveness of a glove’s
chemical permeability. Additionally, only limited breakthrough data for solvent
mixtures is available and in many cases the breakthrough time for a solvent
mixture is considerably less than would be predicted from the individual
breakthrough times for each of the individual solvent components. Finally, batch
variability can also result in wide variations in breakthrough times from one
glove to the next.7 These differences, and possibly greater differences, would
be expected to occur when comparing a similar glove type produced by different
As a result of these limitations, it is necessary that the employer evaluate
glove selection and use to prevent employee exposure as specified in 29 CFR
1910.132(d). Guidance on conducting in-use testing methods for glove selection
Direct Reading Patches/Charcoal Felt Pads
In some instances, direct reading patches and/or bandage-type patches can be
worn inside a glove to demonstrate directly through a color change that an
exposure has occurred. In other instances, charcoal felt patches or bandages can
be worn which can be analyzed by a laboratory to establish the presence of glove
penetration by volatile organic chemicals. These charcoal pads may also be used
for detection of less volatile organic chemicals. However, poor sample
recoveries from a charcoal surface for higher molecular weight substances may
result in underestimating the extent of skin exposure for these types of
When sampling inside a glove, OSHA recommends that employees being sampled wear
disposable gloves inside their normal PPE, with the indicator/charcoal felt pads
being placed on the disposable glove surface. Placing the pad on the disposable
glove between the skin surface and the regular PPE eliminates any potential skin
exposure from the chemicals used in the colorimetric pads, and also reduces any
effects that perspiration might have on the sampling pads.
For inside–the–glove sampling, it also is advisable to use a control pad to
measure the concentration of airborne volatile chemicals. This control pad
should be attached to the employee’s clothing while the employee performs
his/her normal tasks. The glove sample result would then be corrected for the
amount of the organic chemical in the airborne sample to determine the amount of
organic chemical actually permeating the protective glove relative to the amount
of organic chemical entering the glove opening. This procedure, therefore, would
allow the sampler to identify the possible route of glove contamination.
- BIOLOGICAL MONITORING
Biological monitoring is defined by the American Industrial Hygiene Committee on
Biological Monitoring as "the assessment of human exposure through the
measurement of internal chemical markers of exposure, such as the chemical
agent itself and/or one of its metabolites or an exposure related biochemical
change unrelated or related to disease, in human biological samples."9 Biological
monitoring can be a useful technique for determining if dermal exposure is a
significant contributor to the employee's overall exposure. For example, in a
work environment in which the air exposure to a specific chemical is well
controlled, or well characterized, an abnormally elevated biological monitoring
result will likely indicate that skin or ingestion is a major mode of exposure.
Coupled with evidence of surface contamination, and documentation of poor or
non-existent personal protection against chemical skin exposure, biological
monitoring can be a valuable means of documenting dermal exposure to a chemical.
Presently, there are a limited number of guidance values for chemicals measured
in the body. The major sources of these values are published by the ACGIH and
are known as biological exposure indices or BEIs. In addition to the 45
chemicals for which a BEI has been established, the American Industrial Hygiene
Association (AIHA) has developed a BEEL, or biological environmental exposure
level, to more directly develop guidance values for chemicals which have the
skin as their primary mode of exposure. Currently, one chemical,
methylenedianiline (MDA), has an established BEEL.
Finally, there are many studies in peer reviewed literature that report exposure
levels for numerous chemicals measured as biological matrices; these studies
address exposures for employees in a variety of occupations and industries.
These studies can be useful, in a comparative fashion, for assessing the extent
of exposure between exposed and unexposed employees when the workplace in the
study involves the same conditions (e.g., chemical exposure, type of work) as
the workplace being inspected.
A. Guidance on Biological Monitoring Methodology
In the event that a CSHO believes biological monitoring would be valuable to
assess and evaluate employee exposure to a substance or mixture of substances,
they should first contact their Regional office, the Salt Lake Technical Center
and the Office of Occupational Medicine to determine the most effective approach
and technique to obtain the desired result. Biological sampling requires special
consideration and will be addressed on a case–by–case basis.
Biological monitoring results can be used to demonstrate significant skin
absorption, ingestion or airborne exposures. For instance, when wipe/skin
sampling has confirmed exposure, a voluntarily obtained employee biological
sample may prove useful in documenting that skin exposure to the chemical of
concern has occurred. Ideally, it is desirable to have samples from a number of
employees who are suspected of being exposed. Also, control samples from
individuals who do not have skin exposure, or are suspected of much less
exposure, are valuable.
For biological sampling, proper sampling containers and a protocol for handling
and shipping samples need to be addressed. In general, a qualified laboratory
which is experienced in the analysis of biological samples will provide sample
vials, shipping containers, and the technical expertise to properly collect,
store and ship specimens.
B. Review of Employer Biological Monitoring Results
In instances in which an employer has been conducting biological moni¬toring,
the CSHO shall evaluate the results of such testing. The results may assist in
determining whether a significant quantity of the toxic ma¬terial is being
ingested or absorbed through the skin. However, the total body burden is
composed of all modes of exposure (e.g., inhalation, ingestion, absorption and
injection). For the CSHO to assess the results of the biological monitoring, all
the data (including any air monitoring results) must be evaluated to determine
the source(s) of the exposure and the most likely mode(s) of entry.
Results of biological monitoring which have been voluntarily conducted by an
employer should not be used as a basis for citations. In fact, OSHA promotes the
use of biological monitoring by employers as a useful means for minimizing
exposures and for evaluating the effectiveness of control measures.
Citations, in consultation with the Regional Office, would be appropriate when
biological monitoring results indicate an unacceptable level of exposure, and
the employer is unable to demonstrate that meaningful efforts to reduce or
control the exposure(s) were taken.
- WIPE SAMPLING METHODOLOGY
A. Surface Wipe Sampling
Wipe sampling to establish the presence of significant surface contamination is
useful for documenting hazards. A reference control wipe sample or samples taken
from areas in which exposure is not anticipated will also help to establish the
relative amount of surface contamination.
In instances where surface contamination is suspected and the employer has not
required the use of effective Personal Protective Equipment (PPE) for employees
in these areas, wipe sampling may be an effective means of documenting that a
skin hazard exists.
In many instances, several wipe samples taken in an area suspected of being
contaminated may be useful. For example, some surfaces which would be expected
to be contaminated with chemicals because of airborne deposition of a
non-volatile chemical may actually be relatively free of surface contamination
because of frequent contact of the surface by the employee (i.e., frequently
contacted surfaces may be expected to be "clean" because of frequent employee
contact). Wipe samples of frequently contacted surfaces in conjunction with less
frequently contacted surfaces in the same vicinity can be useful to establish
the likelihood that skin exposure is occurring in "clean" areas in which PPE is
not being used, or is being improperly used. Wipe sampling can help establish
that a significant amount of surface contamination is present in areas in which
employees are not effectively protected by PPE.
Housekeeping may also be demonstrated by wipe samples which show major
differences in surface contamination between work areas that have been routinely
cleaned and areas which have not been recently cleaned. This sampling would
allow the CSHO to demonstrate the employer’s failure to maintain a clean work
Wipe samples taken inside the sealing surface of "cleaned" respirators can also
establish the absence of an effective respiratory protection program.
Templates which are used to define a relatively constant surface area for
obtaining a wipe sample are generally not necessary. Templates also cannot be
used except on flat surfaces, and they can cause cross-contamination if the
template is not thoroughly cleaned between each use. Additionally, the CSHO may
want to sample a much larger surface area than the area covered by the template.
This is particularly true if the CSHO wants to determine the cleanliness of a
lunch table or other large surface area. In all cases, the CSHO should measure
the dimensions of the area being sampled and record this value on Form OSHA-91A
because the mass amount of chemical measured by the laboratory will be used to
determine the mass per area for the wipe sample.
B. Skin Sampling
Skin wipe samples taken on potentially exposed areas of an employee’s body are a
useful technique for demonstrating exposure to a recognized hazard. For
water-soluble chemicals, a wipe pad moistened with deionized water can be used
to wipe the skin. Generally, the best procedure is to allow employees to use the
wipe pad to clean their skin surfaces, and then have them insert the wipe pad
into a clean container, which is labeled and sealed. Hands, forearms, faces, and
possibly feet may be exposed to contaminants that a wipe sample of the skin can
be used to establish exposure. Include a blank water sample and use only
deionized water, or another source of water approved by the laboratory, for
- ENFORCEMENT RECOMMENDATIONS
There are currently no surface contamination criteria or quantifications for
skin absorption included in OSHA standards. However, some OSHA standards contain
housekeeping provisions that address the issue of surface contamination.
Exposures to various chemicals (e.g., formaldehyde, methylenedianiline, and
methylene chloride) are addressed in specific standards for general industry,
construction, and shipyard employment. Useful information on dermal exposure
standards can be found at Dermal Exposure - OSHA Standards Safety and Health Topics Page.
Despite the lack of specific criteria or quantitative data for use in the
enforcement of elevated exposures to surface and skin chemical hazards in the
workplace, it is well established that skin exposure and ingestion of chemicals
is a significant mode of occupational exposure. In instances in which a hazard
can be established which is not addressed in a specific OSHA standard, the
compliance officer may consider a 5(a)(1) General Duty Clause citation to
address this concern.
In lieu of issuing a 5(a)(1) citation, it is suggested that alternative
citations can be issued either under OSHA standards addressing sanitation (29
CFR 1910.141), hazard communication (29 CFR 1910.1200), personal protective
equipment (29 CFR 1910, subpart L), exposure to hazardous chemicals in
laboratories (29 CFR 1910.1450), or pertinent standards dealing with
construction (29 CFR 1926) and shipyard employment (29 CFR 1915). In instances
where a high degree of surface contamination is evident, or clear evidence
exists to establish skin exposure of employees to a recognized hazard, then 29
CFR 1910.141(a)(3) can be cited. That is, the CSHO can readily establish that
the employer has failed to keep the workplace "clean to the extent that the
nature of the work allows." Alternatively, 29 CFR 1910.1200(h) can be cited
based upon the evidence collected by the CSHO to demonstrate that the employer
failed to adequately inform and train employees on the hazards present in the
Finally, a specific citation may be issued for deficiencies in PPE use designed
to protect employees from skin exposure under 29 CFR 1910.132, which requires
that the employer evaluate the hazards, select proper PPE, and train employees
on proper use of the PPE.
- Bureau of Labor Statistics. "Nonfatal occupational illnesses by major industry sector and category of illness, private industry, 2006" U.S. Department
of Labor (DOL), 2007 (20 February 2008).
- Boeniger, M.F. Invited Editorial. "The Significance of Skin Exposure." Ann. Occup. Hyg. 47(2003): 591-593.
- VanRooij, J.G.M. et al. "Estimation of Individual Dermal and Respiratory
Uptake of Polycyclic Aromatic Hydrocarbons in 12 Coke Oven Workers." Br. J. Ind.
Med. 50(1993): 623–632.
- Vermeulen, R.; Bos, R.P.; Kromhout, H. "Exposure Related Mutagens in Urine of
Rubber Workers Associated with Inhalable Particulate and Dermal Exposure." Occup.
Environ. Med. 60(2003): 97-103.
- Kanerva, L.et al. Handbook of Occupational Dermatology. Berlin Heidelberg:
Springer – Verlag, 2000.
- Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation
Manual (Part E, Supplemental Guidance for Dermal Risk Assessment), Jul 2004,
EPA/540/R/99/005; OSWER 9285.7-02EP; PB99-963312. (11 December 2007).
- Klingner, T.D. and Boeniger, M.F. "A Critique of Assumptions About Selecting
Chemical-Resistant Gloves: A Case for Workplace Evaluation of Glove Efficacy."
Appl. Occup. Environ. Hyg. 17(2002): 360-367.
- Klingner, T.D. and Boeniger, M.F. "In-Use Testing and Interpretation of
Chemical-Resistant Glove Performance." Appl. Occup. Environ. Hyg. 17(2002):
- Biological Monitoring – A Practical Field Manual. Shane Que Hee, Ed.; AIHA
Publication: AIHA, 2004.
Preloading a group of vials with sampling filters (consult the OSHA Chemical
Sampling Information files to determine appropriate sampling media to use) is a
convenient method to carry the sample media to the worksite. (Smear tabs should
be inserted with the tab end out.) Clean disposable gloves should be worn when
handling the filters and smear tabs. The gloves should not be powdered.
The following are general recommendations for taking wipe samples. Consult the
Chemical Sampling Information files for more specific instructions.
- Record each location where a wipe sample was taken. Photographs, sketches,
and other means of noting sampling locations are helpful.
- A new set of clean, disposable gloves should be used for each sample to avoid
contamination of the filter by previous samples (and the possibility of false
positives) and to prevent contact with the substance.
- Withdraw the filter from the vial with your fingers or clean tweezers. If a
damp wipe sample is desired, moisten the filter with distilled water or other
solvent as recommended. NOTE: For skin sampling use only water. Other solvents
may be appropriate for wiping surfaces depending upon the type of chemical being
- Depending on the purpose of the sample, it may be useful to determine the
concentration of contamination (e.g., in micrograms of agent per area). For
these samples, it is necessary to record the area of the surface wiped (e.g.,
100 cm2). This would normally not be necessary for samples taken to simply show
the presence of the contaminant.
- Firm pressure should be applied when wiping.
- Using the filter, wipe an area about 100 cm2, rubbing the entire area side to
side, then up and down. In many cases (such as knobs and levers) it may not be
possible to wipe 100 cm2.
- Place the filter in a sample vial, cap and number it, and note the number at
the sample location. Include notes which will provide any additional relevant
details regarding the nature of the sample (e.g., "Fred Employee's respirator,
inside"; "Lunch table").
- At least one blank filter treated in the same fashion, but without wiping,
should be submitted for each sampled area.
- Some substances (e.g., benzidine, hexavalent chromium,
4,4'-methylenedianiline) are unstable and may require a solution to be added to
the vial as soon as the wipe sample is placed in the vial or may require other
special sample handling. If such instability is suspected, check the OSHA
Chemical Sampling Information file for sample handling instructions or contact
SLTC for guidance.
- Submit the samples, each sealed with a Form OSHA-21, and in accordance with
procedures located in OTM Chapter 4, to the SLTC with a completed Form OSHA-91A.