OSHA Hazard Information Bulletins
N-Nitroso Compounds in Industry

March 15, 1990




  • Director
  • Office of Field Programs


  • Director
  • Directorate of Technical Support


  • Health Hazard Information Bulletin: N-Nitroso Compounds in Industry

The Directorate of Technical Support issues Hazard Information Bulletin (HIB) in accordance with OSHA Instruction CPL 2.65 to provide relevant information regarding unrecognized or misunderstood health hazards, inadequacies of materials, devices, techniques, and engineering controls. HIBs are initiated based on information provided by the field staff, studies, and reports and concerns expressed by safety and health professionals, employers, and the public. Information is compiled based on a thorough evaluation of available facts, literature and in coordination with appropriate parties. HIBs do not necessarily reflect OSHA policy.

The purpose of this bulletin is to alert field personnel of the potential for amine compounds, used in many industrial processes, to be nitrosated with nitrogen oxides from the air. This bulletin was initiated by the United Rubber, Cork, Linoleum and Plastic Workers of America (URW) who indicated to OSHA their concern about a number of amine compounds that are used in rubber or as rubber additives.

According to the National Institute for Occupational Safety and Health (NIOSH) these amine compounds are considered animal carcinogens. The International Agency for Research on Cancer (IARC) has classified nitrosated amine compounds as Group 2A or Group 2B and the National Toxicology Program (NTP) has designated them as anticipated human carcinogens. Other health effects include effects on the liver, kidney, lungs, bladder, esophagus, skin and eyes. Also, individual substances such as N-Nitrosaminethylamine can produce other symptoms and can include headache, fever, weakness, stomach upsets, enlargement of the liver and jaundice.

Under a contract sponsored by the National Institute for Occupational Safety and Health (NIOSH), a total of 55 on-site plant surveys were conducted in 40 separate United States manufacturing facilities. N-Nitroso compounds were found in 25 of the 40 plants surveyed. The industries where N-Nitroso compounds were found, include the dye industry, rubber industry, fish meal factory, leather industry, manufacturing and users of synthetic metalworking fluids, foundries, and the soap, detergent and surfactant industry. Both the rubber and leather industries were found to have relatively high levels of nitrosamines.


The NIOSH survey of eight plants manufacturing rubber and related products indicated that seven of the facilities were contaminated with one or more of the following compounds:

1- N-Nitrosodiethylamine (NDEA)

2- N-Nitrosodimethylamine (NDMA)

3- N-Nitrosomorpholine (NMOR)

4- N-Nitrosodiphenylamine (NDPhA)

5- N-Nitrosopyrrolidine (NPYR)

NIOSH states that exposures to N-Nitroso compounds occur in many operations in the rubber industry including, Mill Operator, Banbury Operator, Tray Compounder, Extruder Operator, Cure Heater Operator, Mold Press Operator, Press Operator, Laminator, Calendar Operator and others.

NIOSH sampled in a number of rubber plants and found personal exposure levels that range from:

0.1 ug/m3 to 16.0 ug/m3 NDMA, NDEA, NDBA, NMOR; Geauga Company

0.08 ug/m3 to 1.8 ug/m3 NDMA; B.F. Goodrich Company

1.2 ug/m3 to 3.1 ug/m3 NMOR; B.F. Goodrich Company

.005 ug/m3 to .160 ug/m3 NDEA, DMNA, NMOR, NDPhA; Uniroyal, Inc.

0.11 ug/m3 to 1.6 ug/m3 N-Nitrosodiisopropylamine (NDiPA), NDMA, NDPhA, NMOR; Kelly Springfield Tire Co.

0.05 ug/m3 to 0.98 ug/m3 NDMA, NMOR; ST. Clair Rubber Company

In one rubber plant survey, NIOSH reported that levels were below detectable limits for nitrosamine or metabolite biological samples in blood, urine and stool. However, according to NIOSH, the negative findings in the biological samples may reflect the fact that they were collected only during the last two visits of a four visit survey, during which time the airborne nitrosamine levels had been greatly reduced.


NDMA was the primary nitrosamine found associated with the tanning industry with the highest levels being found in those tanneries which used dimethylamine sulfate in the hide unhairing process. Because none of the process water samples or other bulk samples were found to contain significant amounts of any N-Nitroso compounds, NIOSH concluded that worker exposure will occur via inhalation. NIOSH also concluded that the source for the airborne NDMA in these tanneries is due to nitrosation of dimethylamine, in either the gas phase or on surfaces, by airborne oxides of nitrogen.

NIOSH conducted process area/operation air sampling and obtained bulk samples in a number of tanneries and leather plants for N-Nitroso compounds and found:

0.3 ug/m3 to 10.8 ug/m3 NDMA; A.F. Gallun & Son Corp. 0.7 ug/m3 to 3.3 ug/m3 NDMA; Blue Side Tannery. 0.05 ug/m3 NDMA and 0.12 ug/m3 - 0.25 ug/m3 NMOR; Prime Tannery.


In the fish processing industry a small amount (10 ppt to 20 ppt (parts per trillion)) of NDMA was found in air and bulk samples. This may be the result of naturally occurring dimethylamine reacting with either nitrite or atmospheric nitrogen oxides.

During the manufacturing of dyes, nitrite and amines are frequently used and depending upon the dye being manufactured and the type of operation, N-Nitroso compounds may be produced as unwanted by-products. Worker exposure to known N-Nitroso compounds via inhalation in the azo dye industry did not appear to be a serious problem at three plants NIOSH visited. However, not all dye manufacturing processes involving all of the reaction conditions and raw material combinations have been examined by NIOSH.

In the soap, detergent and surfactant industry, the only N-Nitroso compound NIOSH found, in its three plant survey, was NDMA (highest level was 0.8 ug/m3. Airborne dimethylamine, used in the synthesis of some cationic surfactants, may have, according to NIOSH, formed NDMA with ambient levels of nitrogen oxides.

Only one of the five iron and steel casting plants that NIOSH surveyed was found to be contaminated with N-Nitroso compounds. NDMA and NDEA were found within this plant. An amine catalyzed sand core process was in operation at the time of the survey and triethylamine was reported being used. According to NIOSH, this amine, and dimethylamine from an unknown source, may have reacted with the nitrogen oxides being generated by the many combustion sources within the foundry to produce the discovered N-Nitroso compounds.

According to NIOSH, N-Nitrosodiethanolamine (NDE1A) is a known contaminant in metalworking fluids formulated with nitrite and ethanolamines. Therefore, those plants that use these products may have workers exposed to pre-formed NDE1A. Under certain conditions, such as heat, NDE1A can be formed from the precursors present in metalworking fluids.

Currently there are no OSHA Permissible Exposure Limits (PELs) for these amine compounds. OSHA does regulate N-Nitrosodimethylamine under 29 CFR 1910.1016. Use of the OSHA General Duty Clause, 5(a)(1) of the OSHA Act may be considered for other amine compounds. Refer to the OSHA Field Operations Manual (FOM) Chapter IV, A.2.a. for guidance.

At present, OSHA uses Thermosorb/N media or a 15 ml isopropanol bubbler for air sampling and these samples are analyzed by using the Thermal Energy Analyzer (TEA) or High Pressure Liquid Chromatography for most N-Nitroso compounds. OSHA's Salt Lake City Analytical Laboratory (SLCAL) stated that in general there are no problems except for N-Nitrosophenylamine which is unstable in isopropanol used in the bubbler. Bubbler samples must be protected for light during and after sampling. Samples must be either stored in a freezer or analyzed within six days after collection. The limit of detection for most nitrosamines is as low as .02 ug per 75 liter of collected sample, according to the OSHA SLCAL.

OSHA Compliance Officers should be aware of the hazards of N-Nitrosoamine compounds to avoid potential exposures to themselves. Protective clothing, should include gloves, gowns, masks, and goggles, especially in laboratory settings, for the protection of the face, skin, eyes and other parts of the body.

Appropriate compliance action, based on available information, should be taken to ensure that proper engineering controls, work practices, protective clothing and respirators are being utilized. Engineering controls should include process enclosure, local exhaust ventilation and dilution or general ventilation. Isolation of the operation or equipment should also be considered.

OSHA's standard for N-Nitrosodimethylamine requires, as a minimum, that employees be provided with a half-face, filter-type respirator (NIOSH/MSHA approved) for dusts, mists, and fumes, in accordance with 29 CFR 1910.134. Compliance Officers should exercise professional judgement, based on expected exposure and the most current literature findings, in selecting respiratory protection for personal use or in any compliance action for other nitrosamine compounds.

Please disseminate this bulletin to all Area Offices, State Plan States and Consultation Project Officers.


Fine, D.H. 1980. Exposure Assessment to Preformed Environmental N-Nitroso Compounds from the Point of View of our own Studies. Oncology. 37: 99-202.

Fajen, J.M., et al. 1979. N-Nitrosamines in the Rubber and Tire Industry. Science. 205: 1262-1264.

IARC. International Agency for Research on Cancer. N-Nitroso Compounds: Occurrence, Biological Effects and Relevance to Human Cancer in Proceedings of the VIIIth International Symposium, I.K. O'Neill, Editor, IARC Scientific Publication No. 57, pp. 937-942, 1984.

NIOSH, Health Hazard Evaluation Report #HHE 79-126-951, U.S. HHS, CDC, NIOSH; St. Clair Rubber Company, Marysville, Michigan.

NIOSH, Health Hazard Evaluation Report #HETA 79-109-1538, U.S. HHS, CDC, NIOSH; Kelly-Springfield Tire Company, Cumberland, Maryland.

NIOSH, Health Hazard Evaluation Report # TA 80-121-919, U.S. HHS, CDC, NIOSH; Kelly-Springfield Tire Company, Freeport, Illinois.

NIOSH, Health Hazard Evaluation Report # HETA 8l-O45B-l2l6, U.S. HHS, CDC, NIOSH; Uniroyal, Incorporated, Mishawaka, Indiana.

NIOSH, Health Hazard Evaluation Report # HETA 85-003-1834, U.S. HHS, CDC, NIOSH; B.F. Goodrich, Woodburn, Indiana.

NIOSH, Health Hazard Evaluation Report # HETA 81-107-1331, U.S. HHS, CDC, NIOSH; Geauga Company, Middlefield, Ohio.

NIOSH, Industry Wide Study IWS-lO6-l2. In-depth Industrial Hygiene Report of the A.F. Gallum and Son Corporation, Milwaukee, WI. July 22-24, 1980.

NIOSH, Industry Wide Study. Industrial Hygiene Report Survey for N-Nitroso Compounds at Blue Side Tannery, St. Joseph, MO, January 16, 1979.

NIOSH, Survey for N-Nitroso Compounds at Prime Tannery, Berwick, ME, February 5, 1979.

NIOSH, Industry Wide Report IWS-72.32, U.S. HHS, NIOSH; Survey for N-Nitroso Compounds at Oaks Tire Plant, B.F. Goodrich Company, Oaks, Pa., January 23, 1979.

NIOSH Pocket Guide to Hazardous Chemical Hazards, #85-114, 1986. U.S. HHS, NIOSH

NIOSH Technical Report # 83-114, U.S. HHS, CDC NIOSH; N-Nitroso Compounds in the Factory Environment, June 1983.