Occupational Chemical Exposures

The assessment which is undertaken by NICNAS covers the assessment of the health and aquatic toxicity hazards of the chemical, occupational exposure, public exposure and environmental exposure and fate. A risk assessment is performed and recommendations are made to control and minimise the risks. The results of the assessment are published in a report which is made available to the public via the NICNAS Web site [3]. 

Evaluations of occupational exposure to physical agents such as noise, radiation or heat, biological agents, and multiple chemical agents are similar to the process for single chemical substances but have some key differences. 

The effects of occupational exposure to lindane have been investigated extensively (96—100). These studies indicated that occupational exposure to lindane resulted in increased body burdens of this chemical however, toxic effects associated with these exposures were minimal and no central nervous system disorders were observed. This is in contrast to the polyneuropathies that are often observed after exposure to other haloorganic solvents. 

The toxicity of a substance is its capacity to cause injury once inside the body. The main modes of entry into the body by chemicals in industry are inhalation, ingestion and absorption through the skin. Gases, vapours, mists, dusts, fumes and aerosols can be inhaled and they can also affect the skin, eyes and mucous membranes. Ingestion is rare although possible as a result of poor personal hygiene, subconscious hand-to-mouth contact, or accidents. The skin can be affected directly by contact with the chemicals, even when intact, but its permeability to certain substances also offers a route into the body. Chemicals accorded a skin notation in the list of Occupational Exposure Limits (see Table 5.12) are listed in Table 5.2. Exposure may also arise via skin lesions. 

TQXiGITY AND RISKS INDUCED BY OCCUPATIONAL EXPOSURE TO CHEMICAL COMPOUNDS... 

Occupational and environmental exposure to chemicals can take place both indoors and outdoors. Occupational exposure is caused by the chemicals that are used and produced indoors in industrial plants, whereas nonoccupa-tional (and occupational nonindustrial) indoor exposure is mainly caused by products. Toluene in printing plants and styrene in the reinforced plastic industry are typical examples of the two types of industrial occupational exposures. Products containing styrene polymers may release the styrene monomer into indoor air in the nonindustrial environment for a long time. Formaldehyde is another typical indoor pollutant. The source of formaldehyde is the resins used in the production process. During accidents, occupational and environmental exposures may occur simultaneously. Years ago, dioxin was formed as a byproduct of production of phenoxy acid herbicides. An explosion in a factory in... 

Skin is also important as an occupational exposure route. Lipid-soluble solvents often penetrate the skin, especially as a liquid. Not only solvents, but also many pesticides are, in fact, preferentially absorbed into the body through the skin. The ease of penetration depends on the molecular size of the compound, and the characteristics of the skin, in addition to the lipid solubility and polarity of the compounds. Absorption of chemicals is especially effective in such areas of the skin as the face and scrotum. Even though solid materials do not usually readily penetrate the skin, there are exceptions (e.g., benzo(Lt)pyrene and chlorophenols) to this rule. 

As stated earlier, inhalation is the main route of absorption for occupational exposure to chemicals. Absorption of gaseous substances depends on solubility ifi blood and tissues (as presented in Sections 2.3.3-2.3.5), blood flow, and pulmonary ventilation. Particle size has an important influence on the absorption of aerosols (see Sections 2.3.7 and 3.1.1). 

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