Cancer carcinogenic mixtures

Formaldehyde is a major contributor to many cases of sick building syndrome. It is a very toxic chemical that is corrosive to the skin, eyes, and the respiratory system. Acute or chronic exposure can result in difficulty breathing and even brief exposures can induce asthmatic reactions in sensitized individuals. 13 Exposures to mixtures of formaldehyde and lipophilic chemicals can result in unanticipated toxic effects. 14 Formaldehyde is an animal carcinogen, a suspected human nasal cancer carcinogen 29 and suspected human leukemogen. 3°1... 

Virtually all of these occupations entail exposure to mixtures of chemicals with the carcinogenic agent(s) unidentified. Indeed, it is the mixtures, and not any particular components of them, that are cancer causing. Examples of carcinogenic mixtures of occupational chemicals are given in the next section. 

In a manner analogous to the hazard index approach for noncarcinogens, hazard quotients for carcinogenic mixture components can be estimated by dividing chemical exposure levels by doses (DR) associated with a set level of cancer risk the HI is the sum of the HQ values [9,16] ... 

Polycyclic aromatic hydrocarbons have been classified as human carcinogens because they induce cancers in experimental animals and because smoking and exposure to mixtures of chemicals containing polycyclic aromatic hydrocarbons in the workplace increase the risk of lung cancer in exposed individuals. In experimental animals, benzo(a)pyrene induces cancer in different organs depending on the route of administration.Furthermore, exposure to polycyclic aromatic hydrocarbons commonly occurs in occupations related to traffic (use of diesel engines in transportation and railways). 

There is no evidence that exposure to //-hexane increases the risk of cancer in people. No reliable information is available on whether //-hexane causes cancer in animals. In an animal experiment with commercial hexane (which contains //-hexane), an increase in liver cancer was found in female mice after exposure for 2 years. No increase was found in male mice or in rats of either sex. Commercial hexane is a mixture, and we do not know what parts of the mixture caused the cancer in the female mice. //-Hexane has not been characterized for carcinogenicity by the Department of Health and Human Services (DHHS), the International Agency for Research on Cancer (IARC), or the Environmental Protection Agency (EPA). 

According to OECD (2001b), the term carcinogen denotes a chemical substance or a mixture of chemical substances, which induce cancer or increase its incidence. Substances which have induced benign and malignant tumors in well-performed experimental studies on animals are considered also to be presumed or suspected human carcinogens unless there is strong evidence that the mechanism of tumor formation is not relevant for humans. ... 

Welders are typically exposed to a complex mixture of dust and fume of metallic oxides, as well as irritant gases, and are subject to mixed-dust pneumoconiosis with possible loss of pulmonary function this should not be confused with benign pneumoconiosis caused by iron oxide. Although an increased incidence of lung cancer has been observed among hematite miners exposed to iron oxide, presumably owing to concomitant radon gas exposure, there is no evidence that iron oxide alone is carcinogenic to man or animals. ... 

Increased cancer mortality has been associated with exposure to the PAH present in used metal-work cutting oils and mineral oils. The carcinogenic potential of these complex mixtures was related to their PAH... 

The presence in mineral oil of potential carcinogens also raised safety concerns relating to FCA/FIA. Mineral oil is composed of a complex mixture of both cyclic and non-cyclic hydrocarbons of varying chain length, some of which display carcinogenic potential. Arlacel A was also found to be capable of inducing cancer in mice. 

Sufficient evidence of carcinogenicity. The Working Group considers that a causal relationship has been established between exposure to the agent, mixture or exposure circumstance and human cancer. That is, a positive relationship has been observed between the exposure and cancer in studies in which chance, bias and confounding could be ruled out with reasonable confidence. 

Considering the insensitivity of the decaBDE studies for MRL derivation, as well as the lack of cancer information on the lower brominated PBB mixtures that may have higher carcinogenic potency than decaBDE, there is a need for chronic toxicity studies on pentaBDE and/or octaBDE. Evaluations that include the thyroid would be particularly informative because the acute and intermediate-duration animal studies indicate that the thyroid is a particularly sensitive target organ for PBDEs. 

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