Thomas McDonald

Levels of the polybrominated diphenyl ethers (PBDEs), a class of widely used flame retardants, appear to be rising rapidly in human tissues, as evidenced by studies of human breast milk. The case of the PBDEs illustrates the value of breast-milk monitoring programs in identifying important emerging pollutants, and highlights why such monitoring programs are needed in the United States. A review of the use, occurrence, and toxicity of PBDEs indicates many parallels between some PBDEs, PCBs, and other polyhalogenated persistent organic pollutants, and suggests that the PBDEs may be a significant environmental challenge in the future.

Brominated flame retardants (BFRs) are widely used in polymers and textiles and applied in electronic equipment, construction materials, and furniture for the purpose of fire prevention. BFRs with the highest production volume are tetrabromobisphenol A (TBBPA), 1,2,5,6,9,10- hexabromocyclododecanes (HBCDs: α-HBCD + β-HBCD + γ-HBCD), and polybrominated diphenyl ethers (PBDEs). Several BFRs are highly lipophilic persistent organic pollutants (POPs) which have been identified in the aquatic and terrestrial environment including wildlife and humans. In exposed organisms including humans toxic effects, bioaccumulation, metabolism, and phannacokinetics (especially half-life t<sub>1/2</sub>) are important criterions in the hazard assessment.<br />The aim of the present study was to estimate the terminal elimination half-lives (t<sub>1/2H</sub>) of the main BFRs from the whole body (also named body-burden half-life) and/or from the adipose tissue (fat) of adult humans. The t<sub>1/2H </sub>data for the following BFRs were evaluated: TBBPA, HBCD, 2,2 ',4,4' - tetrabromodiphenyl ether (BDE-47), 2,2' ,4,4' ,5-pentaBDE (BDE-99), 2,2' ,4,4' ,6-pentaBDE (BDE100), 2,2',4,4',5,5'-hexaBDE (BDE-153), and 2,2' ,4,4',5,6-hexaBDE (BDE-154).

Recent analyses have revealed that 38% of municipal sources of drinking water in California have detectable levels of hexavalent chromium. This observation provided new impetus to characterize the carcinogenic risk associated with oral exposure to hexavalent chromium in drinking water. Notwithstanding the well-characterized increases in cancer associated with inhalation exposure to this chemical, the marked reduction of hexavalent chromium to trivalent chromium in the stomach suggests that exposure to hexavalent chromium in drinking water may not pose a carcinogenic risk. A reevaluation of studies that investigated the toxicokinetics, the genotoxicity, and the mechanism of carcinogenicity of hexavalent chromium, as well as the available human and animal cancer studies, was undertaken to determine if there is evidence that exposure to this chemical in drinking water may pose a carcinogenic risk. Mechanistic studies suggest the potential for a carcinogenic response if hexavalent chromium enters cells. Both toxicokinetic and genotoxicity studies indicate that a portion of an orally administered dose of hexavalent chromium is absorbed and gets into cells of several tissues, causing DNA damage. The only lifetime oral study of hexavalent chromium in animals conducted thus far yielded a statistically significant increase in stomach tumors compared to controls. Also, in a limited-term cancer study, co-exposure to hexavalent chromium in drinking water and ultraviolet light produced skin tumors in mice. The only available cancer study of humans exposed to hexavalent chromium in drinking water revealed a statistically significant increase in stomach tumors. Moreover, a meta-analysis of occupational studies also revealed a statistically significant increase in stomach cancers. The increases in stomach tumors in both human and animal studies, along with the toxicokinetic, genotoxic, and mechanistic data, suggest that oral exposure to this agent appears to pose a carcinogenic risk.

OBJECTIVE: To study the medical and socioeconomic impact of Wegener's granulomatosis (WG) in a large cohort (n = 701) of patients who are members of the international WG Support Group (WGSG). METHODS: Forty questions designed and validated by one of the authors and reviewed by the medical consultants of the WGSG International were mailed to 1690 patients with WG who are members of the WGSG; 701 (41%) patients returned the questions. Diagnosis of WG was self-reported for purpose of this questionnaire. Study domains included demographic features, education, analysis of categories of medical care providers, organ system involvement, delay in diagnosis, frequency and sites of biopsies to assist in diagnosis, treatment outcome, familial association, disability, and financial effect. We compared some of these features in patients whose diagnosis was made in the 1970s, 1980s, or 1990s. RESULTS: In our cohort WG was slightly more prevalent in women (56%), particularly if the disease started at a younger age (9-40 years). Peak age period at disease onset was 45-65 years. Ninety-eight percent of patients were Caucasian. Diagnosis of WG was usually made by a specialist, and the majority of patients received subsequent care by specialists. During the past decade only 7% of patients received a diagnosis of WG upon their first visit to a physician. A period of 3-12 months passed from onset of features of WG to achieving a diagnosis in the majority of patients. Compared to the period 1970-90, in recent years fewer patients had biopsies performed for diagnostic purposes. This observation correlated with increased use of antineutrophil cytoplasmic antibodies. In the 1990s the most common reported therapy was combination of corticosteroids and cyclophosphamide (73%). Patients also reported initial therapy with methotrexate (11%), trimethoprim-sulfamethoxa-zole (32%), and azathioprine (5%). Patients rarely reported other family members with WG. In none of 12 WG patients who had a twin did the twin have WG. The survey did not identify any specific environmental exposure, occupation, or hobby that was overrepresented among patients. One hundred seventy-nine WG patients reported that their disease had a significant financial impact on their lives. CONCLUSION: Information from this survey of 701 patients is consistent with physician reported data about organ involvement, initial manifestations and therapy, and outcomes in WG. More WG patients in the 1990s were diagnosed after first physician encounter. This survey did not reveal any predisposing or inducing environmental or familial factors, and showed fewer patients become disabled and more were able to work full time.