Occupational exposure limit origins

Current Intelligence Bulletin 63 Occupational Exposure to Titanium Dioxide "may be the first document (originally released for external review as a draft in 2005) to recommend separate occupational exposure limits for the same material based on particle size," according to Vladimir Murashov, Ph.D., special assistant for nanotechnology to the NIOSH Director. 

Borak J. The beryllium occupational exposure limit historical origin and current inadequacy. J Occup Environ Med 2006 48(2) 109-116. 

Several epidemiology studies on occupational exposure to 1,4-dioxane are available in the literature. Very limited conclusions can be drawn from the negative findings of these studies. All of the studies lack sufficient cohort size and number of cases to enable identification of low-level excess cancer risk. Of note, the reported cancers have various sites of origin and are not similar to those seen in animal models. A mortality study was conducted on employees exposed to 1,4-dioxane. Observed deaths from overall cancer were not significantly different from expected number of deaths. 1,4-Dioxane can be inhaled in amounts sufficient to cause serious systemic intoxication. Injury may become apparent hours after termination of an exposure that had been erroneously considered to be negligible. Prolonged and repeated contact can cause eczema and repeated inhalation exposures to low concentrations have been fatal. 

However, since reliable data on exposure levels were not available, it is impossible to establish a dose-response relationship or a NOAEL. In addition, coronary heart disease has a multicausal origin that is in part related to the saturated fat intake of the population and is also influenced by a large number of other risk factors such as smoking, other dietary habits, diabetes, and physical inactivity. A combination of two or more risk factors greatly increases the incidence of coronary heart disease, and therefore carbon disulfide may be a cofactor in the presence of other risk factors (WHO 1979). Another limitation with occupational studies reported from the viscose rayon industry is concurrent exposure to other chemicals such as hydrogen sulfide (Hemberg et al. 1970 Rubin and Arieff 1945 Swaen et al. 1994 Tolonen et al. 1979). 

This chapter deals with exposure to common organic solvents which are used in large quantities to dissolve fats, resins, and other materials. Very dangerous chemicals, such as benzene, which are no more used as solvents due to their toxic properties, will not be discussed even though they may have had extensive uses as solvents earlier and even though those may be still important chemicals as petroleum components or as intermediates for other chemicals. Also, solvents with very specialized uses, such as carbon disulfide the use of which is practically limited to viscose rayon industry and laboratories, are only shortly considered. Exposure data presented originate mainly from literature however, some unpublished data obtained from the Finnish Institute of Occupational Health (FIOH) has been added to indicate the order of magnitude of current exposure levels in industrialized countries (data cover the years 1994-1996). 

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