Arsenic risk assessment.

Abstract

The brillant literature review and health risk assessment by Mennear and ChengChung, "Polybrominated Dibenzo-p-dioxins and Dibenzofurans: Literature Review and Health Assessment" [EHP 102(suppl 1):265-274], states that "reports of human toxicity associated with exposure to PBDDs and PBDFs were not found" (p. 272). In fact, in their review, no references are discussed or quoted regarding human studies.Two papers have been published on the human toxicology of these compounds. The first (1) is a recent report, previously presented at the Dioxin '90 Congress (2), about a chemist who was exposed to 2,3,7,8,-tetrabromodibenzodioxin (TBDD) and to 2,3,7, in March and September 1956, respectively, when synthesizing these chemicals. The chemist was defined as "in good health" in 1990, when determinations of chlorinated and brominated dioxins and dibenzofurans were performed on whole blood. High concentrations of several congeners were detected, and the results were used to discuss the half-life of the chemicals in humans. The subject presented a mild chloracne after an unspecified time from his exposure to bromodixoins in March, suggesting that TBDD could produce skin effects as chlorodioxins. Other more relevant symptoms occurred after the exposure to TCDD in September, and the patient was hospitalized for a short period.The second was a study of subjects exposed to PBDDs and PBDFs as a result of working at a BASF factory in etrusion blending of polybutyleneterphthalate with decarbromodiphenyl ether, used as a flame retardant. The intensity of exposure was determined in 1989 through air monitoring (3). The paper presents blood levels of 2,3,7,8,-TBDF and TBDD and of total congener profiles for some exposed workers and the results of a comparison of several immunological tests in a population of exposed versus a population of unexposed deriving from the same working cohort. Workers had detectable blood levels of TBDD and TBDF; half-life estimates of these chemicals are presented. The results of immunological tests were described as "not adversely impacted at these burdens of PBDFs and PBDDs," even though the results of several tests showed a correlation with exposure, and in the subject having the highest blood levels of PBDFs and PBDDs, immunological changes were quite relevant. The authors stated that clinical examination did not reveal "skin lesions consistent with an acnegenic response.It should be stressed that the results of the two quoted articles do not change the conclusions of Mennear and ChengChung on the health risks of PBDDs and PBDFs. However, slightly different suggestions for future research can be derived. Human populations have been or are exposed to these chemicals because of their use in several work processes involving flame retardants, environmental exposures (mainly due to municipal incinerators), or because of accidents due to thermal decomposition of flame retardants. These exposed human populations can be suitable, at least in theory, for toxicological and epidemiological observations.

Toxicological profile for arsenic

“…The use of a cancer risk estimate derived from the Tseng et al (1968) study for a U.S. population has been the source of intense debate. Some have argued and have provided data in support of the view that there is persuasive evidence that inorganic arsenic is a cause of human cancer at several sites (i.e., Smith et al 1992Smith et al , 1995Smith et al , 2002. On the other hand, a number of concerns have been raised regarding the strength, or lack of strength, of the database, including: the adequacy of the model used by EPA and the accuracy and reliability of the exposure data (Brown et al 1997a(Brown et al , 1997b; a number of host and environmental factors among the Taiwanese not applicable elsewhere (Carlson-Lynch et al 1994); a possible threshold for arsenic carcinogenicity and nonlinearities in the dose-response curve (Abernathy et al 1996;Slayton et al 1996); differences in health and nutrition between Taiwan and the United States…”