CARCINOGENICITY Of CHROMIUM AND CERTAIN CHROMIUM COMPOUNDS
PROPERTIES
Chromium is an odorless, steel-to-semi-grey, lustrous metal available as crystals or powder (99.97% purity). It is insoluble in hot and cold water, nitric acid, and aqua regia, but reacts with dilute sulfuric acid and hydrochloric acid. Calcium chromate occurs in the form of yellow monoclinic prisms. It is soluble in cold and hot water and reacts with acids and ethanol. Chromium trioxide is odorless, dark-purplish-to-red-rhombus crystals that are deliquescent. It is soluble in alcohol, ethanol, sulfuric acid, and nitric acid. When heated to decomposition, chromium trioxide emits smoke and irritating fumes. Lead chromate occurs as yellow or orange monoclinic crystals that are insoluble in water, acetic acid, and ammonia but are soluble in acid and alkali. Lead chromate, when heated to decomposition, emits toxic fumes of lead. Basic lead chromate is a red amorphous or crystalline powder. It is insoluble in hot and cold water, reacts with most acid and alkali but not with acetic acid or ammonia, and emits very toxic fumes of lead when heated to decomposition. Strontium chromate occurs as monoclinic yellow crystals. It is soluble in cold and hot water and reacts with hydrochloric acid, nitric acid, acetic acid, and ammonium salts. Zinc chromate occurs as lemon yellow prisms. It is insoluble in cold water and acetone, dissolves in hot water, and is soluble in acid and liquid ammonia.
EXPOSURE AND HAZARDS
There is inadequate evidence for the carcinogenicity of chromium and most trivalent chromium compounds in experimental animals. There is sufficient evidence for the following hexavalent chromium compounds in experimental animals: calcium chromate , chromium trioxide , lead chromate , strontium chromate , and zinc chromate . Calcium chromate produced bronchial carcinomas after implantation of an intrabronchial pellet in rats and injection-site sarcomas after intramuscular implantation in rats and mice and after intrapleural injection in rats. Bronchial carcinomas were produced in rats after intrabronchial implantation of strontium chromate and zinc chromate. Injection-site sarcomas were produced in rats and mice after intramuscular, intrapleural, and subcutaneous injections of chromite ore, strontium chromate, chromium trioxide, lead chromate, and zinc chromate, but few or no sarcomas were induced by barium chromate , sodium chromate, sodium dichromate , or chromic acetate .
There were no adequate data available to evaluate the carcinogenicity of chromium and trivalent chromium compounds in humans; however, they also concluded that there was sufficient evidence for the carcinogenicity of hexavalent chromium compounds in humans . An increased incidence of lung cancer has been observed among workers in both the bichromate-producing industry and chromate-pigment manufacturing. There is evidence of a similar risk among chromium platers and chromium-alloy workers. The incidences of cancers at other sites may also be increased in such populations. However, a clear distinction between the relative carcinogenicity of chromium compounds of different oxidation states or solubilities has been difficult to achieve. Recent studies of chromate-pigment makers and users, chrome platers, welders and chrome-alloy foundry workers have shed some light on this problem. For chromate-pigment makers and users, respiratory cancer excesses have usually been found. Chromium pigments are usually hexavalent and commonly include zinc, lead, or strontium chromate. Chrome platers have also been found to have excess lung cancer. Stainless steel welding involves the greatest exposure to hexavalent chromium, as well as to nickel, and one study of chromium-nickel alloy foundry workers showed a statistically significant excess of lung cancers.
CARCINOGENICITY OF VINYL CHLORIDE
PROPERTIES
Vinyl chloride is a colorless, flammable gas with a faintly sweet odor. The gas polymerizes in light and liquifies in a freezing mixture. It is slightly soluble in water, soluble in ethanol, and very soluble in ether, carbon tetrachloride, and benzene. In the form of vapor, vinyl chloride is a dangerous fire and severe explosion hazard when exposed to heat, flame, or oxidizers. On standing, it forms peroxides in air and
can then explode. On combustion, it is degraded mainly to carbon dioxide, carbon monoxide, hydrogen chloride, and traces of phosgene. Technical-grade vinyl chloride is commercially supplied as 99.9% pure liquid under pressure.
USE
Vinyl chloride is industrially important because of the inherent flame retardant properties of its polymer, its wide variety of end use products, and the low cost of producing polymers from it . Vinyl chloride monomer is the parent compound of polyvinyl chloride (PVC), a plastic resin used in innumerable consumer and industrial products, including containers, wrapping film, battery cell separators, electrical insulation, water distribution systems (water and drain pipes, hose), flooring, windows, phonograph records, videodiscs, irrigation systems, and credit cards. Vinyl chloride-vinyl acetate copolymers are used extensively to produce vinyl-asbestos floor tiles.
EXPOSURE
The primary routes of potential human exposure to vinyl chloride are inhalation and dermal contact. Potential human exposure to vinyl chloride occurs in the workplace, through general air and water pollution, and to a limited extent, from the use of fabricated products The major source of releases of vinyl chloride into the environment is believed to be emissions and effluents from plastics industries. Most of the vinyl chloride released into the environment will eventually locate in the atmosphere while much smaller amounts will eventually locate in ground water. Segments of the general population living in the vicinity of emission sources are potentially exposed to vinyl chloride by inhalation of contaminated air.The majority of the general population is not expected to be exposed to vinyl chloride through ingestion of drinking water but where people have PVC water pipes that have not been treated adequately to remove vinyl chloride monomer,the risk lies .
There is sufficient evidence for the carcinogenicity of vinyl chloride in humans.Vinyl chloride has been associated with tumors of the liver, brain, lung etc A large number of epidemiological studies and case reports have substantiated the causal association between vinyl chloride and angiosarcoma of the liver. Exposure to polyvinyl chloride dust was associated with an increased incidence of lung tumors in one study; the authors suggested that trapped vinyl chloride monomer was responsible. Melanoma occurred in excess in one study but has not been mentioned in others. Slightly elevated risks for gastric and gastrointestinal cancer (other than liver cancer) were indicated in some studies, but these were not confirmed in others.
Those were some of really hazardous chemicals in common use .But apart from these there are more common household hazards especially OTC(Over the counter) Medications ,which can be stocked in all cabins .Children are vulnerable to such hazards as they find the attractive coloring of such medications .The best way to prevent poisonings is to make it impossible for young children to find and get at medications and poisonous products.