Isocyanates occupational exposure

National Institute for Occupational Safety and Health Criteria for a Recommended Standard. . . Occupational Exposure to Di-isocyanates. DHEW (NIOSH) Pub No 78-215. Washington DC, US Government Printing Office, 1978... 

Prepolymeric HDI-BT paint formnlations, which generally contain 1% monomeric HDI, are now widely used for coatings applications, particularly in the automobile and airplane industries (Alexandersson et al. 1987 Karol 1986 Key-Schwartz 1992 Nielson et al. 1985 Rosenberg and Savolainen 1986 Rosenberg and Tuomi 1984). Consequently, many reported occupational exposures to HDI are actually exposures predominantly to HDI-BT (Karol 1986 Karol and Hauth 1982). Although isocyanate prepolymers are safer to use than the free monomers, primarily because of their lower vapor pressures, they can still pose a health risk to workers when inhaled in the aerosol form (Karol and Hauth 1982 Rosenberg and Tuomi 1984). There... 

The risk of cancer associated with occupational exposure to isocyanates has been examined in three industrial cohort studies and in a population-based case-control study of several types of cancer. No strong association or consistent pattern has emerged. 

Uses Aniline is an oily liquid used in the manufacture of dyestuffs, intermediates for dyestuffs, and manufacture of rubber accelerators and antioxidant substances. Aniline has been extensively used as an intermediate in the manufacture of plastics, pharmaceuticals, pesticides, isocyanates, and hydroquinones. Occupational exposure to aniline is extensive and as diverse as its industrial uses. Workers associated with the manufacturing of acetanalide bromide, coal tar, colors and dyes, leather, disinfectants, nitraniline, perfumes, rubber, and photographic materials become victims of adverse effects from aniline. 

Fuchs et aK (1) published observations on an asthmatic syndrome in seven out oT nine persons exposed to TDI. In 1953, Reinl (2) reported cases of respiratory problems in 17 workers exposed to TDI and/or other isocyanates 13 of these cases were severe and death of one was attributed to occupational exposures. 

The fact that these concentrations have been measured does not mean that occupational exposures occur persons may use respiratory protection equipped to prevent exposure. All persons who have excessive occupational exposure to isocyanates may experience primary irritant effects in the respiratory tract depending on the extent of excessive exposure. Brief accidental exposures to concentrations of isocyanates tenfold or more above the TLV may cause short term respiratory irritation with recovery 24-48 hours following cessation of exposure. Continuing repeated workday exposures several-fold higher than the TLV can cause chronic respiratory irritation. All individuals will not suffer the same degree of respiratory irritation from excessive exposures due to individual biochemical and physiological differences. Studies have shown that on the order of five percent of persons who have had an occupational exposure to TDI develop a bronchial asthmatic type of response to subsequent exposures that are below concentrations causing any detectable primary irritation. 

In summary, the major potential occupational health problem from excessive exposure to isocyanates is primary respiratory irritation. A fraction of workers exposed may develop a bronchial asthmatic reaction to isocyanates and there appears to be some cross reactivity. The most extensive study, including preexposure baseline respiratory function measurements, has provided data indicating that keeping exposures to TDI below 0.02 ppm (0.14 ug/ m3) appears to prevent decrement in respiratory function. There are less data on exposures and respiratory function of workers using other isocyanates. Isocyanates such as MDI are less volatile than TDI. There is less potential for exposure to vapors of the lower volatility isocyanates, but exposures to vapor and to particulates can occur and exposures to all isocyanates do need to be controlled in order to protect workers. 

Carroll KB, Secombe CJP, Pepys J (1976) Asthma due to non-occupational exposure to toluene (tolylene) di-isocyanate. Clin Allergy 6 99-104 Cattalini L, Martelli M (1967) Relazione tra reattivita di complessi planari del platino e na-tura del grouppo uscente, in reazioni di sostituzione nucleofila. Gazz Chim Ital 97 498-508... 

U.S. Department of Health, Education, and Welfare (1973) Occupational exposure to toluene di-isocyanate. U.S. Government Printing Office, Washington, DC Vallery-Radot L, Blamoutier R (1929) Sensibilisation au chloroplatinite de potassium accidents graves de choc survenus a la suite d une cutireaction avec ce sel. Bull Soc Med Hop Paris 45 222-230... 

Phosgene is said to be probably the most poisonous gas used in industry. However, hydrogen sdenide is probably a more poisonous gas and methyl isocyanate is certainly a more poisonous vapor (bp 39 °C). Bis(chloromethyl) ether is more poisonous in the chronic sense (Occupational Exposure Limit, OEL, 1 ppb). Phosgene might, therefore, be more correctly described as the most poisonous gas used in any significant volume in industry [1],... 

Meredith, S.K., Bugler, J., and Clark, R.L., Isocyanate exposure and occupational asthma a case-referent study, Occup. Environ. Med., 57, 830, 2000. 

Avashia B, Battigelli MC, Morgan WKC, et al Effects of prolonged low exposure to methyl isocyanate. J Occup Environ Med 38(6) 625-630, 1996... 

Brorson T, Sharping G, Nielsen J. 1990b. Biological monitoring of isocyanates and related amines. 11. Test chamber exposure of humans to 1,6-hexamethylene diisocyanate (HDl). Int Arch Occup Environ Health 62(5) 385-389. 

Redlich, C.A., Bello, D., and Wisnewski, A.V. (2006) Isocyanate exposures and health effects, Environmental and Occupational Medicine, in (eds W. Rom and S. Markowitz), Wolters Kluwer/Lippincott... 

In the Montreal case-control study carried out by Siemiatycki (1991) (see monograph on dichloromethane in this volume), the investigators estimated the associations between 293 workplace substances and several types of cancer. Isocyanates were one of the substances, and it was stated that the most common form in this study was toluene diisocyanates. The main occupations to which isocyanate exposure was attributed in this study were motor vehicle refinishers, motor vehicle mechanics and foundry workers. Only 0.8% of the study subjects had ever been exposed to isocyanates. For most types of cancer examined (oesophagus, stomach, colon, rectum, pancreas, prostate, bladder, kidney, skin melanoma, lymphoma), there was no indication of an excess risk due to isocyanates. For lung cancer, in the population subgroup of French Canadians (the majority ethnic group in this region), based on 10 cases exposed at any level, the odds ratio was 2.2 (90% CI, 0.9-5.3). [The interpretation of the null results has to take into account the small numbers and presumably low exposure levels. Workers had multiple exposures.]... 

Isocyanate-induced asthma and hypersensitivity pneumonitis in humans have been reviewed (Baur, 1995 Bernstein, 1996). A case of fatal asthma of a 4,4 -mcthylcncdiphcnyl diisocyanate-scnsitized subject has been described (Carino et al., 1997). Exposure to 4,4 -methylenediphcnyl diisocyanate is a frequent cause of occupational asthma (Liss et al., 1988 Vogelmcicr et al., 1991 Bernstein et al., 1993) but may also induce hypersensitivity pneumonitis (Malo Zeiss, 1982 Vandenplas et al., 1993) and inflammatory upper respiratory tract diseases (Liss et al., 1988 Littorin et al., 1994). Most patients with 4,4 -methylenediphcnyl diisocyanate-induced asthma have elevated levels of IgG-class antibodies towards 4,4 -methylenediphenyl diisocyanate-albumin conjugates in the plasma, while IgE-class antibodies are rare (Liss et al., 1988). 

Mark Cullen is professor of medicine and public health at Yale University School of Medicine. His research interests are in occupational and environmental medicine, including isocyanate exposure in automobile-shop workers, lung cancer in people exposed to asbestos, and lead toxicity in workers. He has published several textbooks, including Clinical Occupational Medicine and Textbook of Clinical Occupational and Environmental Medicine. Dr. Cullen received his MD from Yale University and did his residency in internal medicine. He is a member of the DuPont Epidemiology Review Board, a member of the MacArthur Foundation Network on Socioeconomic Status and Health, and a corporate medical director for the Aluminum Company of America. Dr. Cullen is a member of the Institute of Medicine and served as a member of its Board on Health Sciences. 

Aromatic amines are used in the manufacture of rubber chemicals, drugs, dyes, isocyanates, and many other miscellaneous chemical products. The toxicity of aromatic amines has been known and studied for many yearsfH They all penetrate the skin and all produce methemoglobinemia. .) Recently, the Occupational Safety and Health Administration (OSHA) established exposure limits for 14 human carcinogens, several of which are aromatic amines(3)... 

This paper describes a procedure for measuring the exposure of personnel to methyl isocyanate (MIC) in air in the occupational environment. The ion exchange adsorbent, together with the high-performance liquid chromatographic procedure as written, is capable of detecting 238 ng of MIC per milliliter. This is equivalent to 0.01 parts per million in a 15-liter air sample volume. 

Occupational hazards (e.g. exposure to reactive chemicals such as isocyanates or IgE-related, such as allergens from animals, flour and grain). 

By the year 1956, more than 100 cases of illnesses and four cases of death due to poisoning by TDI were reported (Baader, 1956). In view of the increased use of isocyanates, the National Institute of Occupational Safety and Health, USA, projected as early as 1978 that approximately 50,000 to 100,000 workers would be exposed to these chemicals within 2 years (NIOSH, 1978) this estimate was based on exposure at the workplace in polyurethane production, upholstery work, wire coating, and spray painting in the absence of any accidental spill (Axford et al, 1976 Editorial, 1966 Fuchs and Valade, 1951 Hill, 1970 Williamson, 1965). 

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