Characteristics of Disease and Some Exposure Considerations

Retrospective assessment of exposure to chemicals for a microelectronics and business machine manufacturing facility

A retrospective exposure assessment was performed for use in a health outcomes study of a facility manufacturing circuit boards, business machines, and other equipment during the years 1969-2002. A matrix was developed identifying chemical use by department-year based on company-provided information. Use of six chemical agents (fiberglass, lead, methylene chloride, methyl chloroform, perchloroethylene, and trichloroethylene) and six chemical classes (acid-base, aromatic hydrocarbons, chlorinated hydrocarbons, other hydrocarbons, chlorofluorocarbons, and metals), and general (including unspecified) chemicals was identified. The matrix also contained an assignment for each department-year categorizing the potential for use of chemicals as negligible, intermittent/incidental, or routine. These department-based exposure matrix data were combined with work history data to provide duration of potential chemical use for workers. Negligible, intermittent/incidental or routine extent-of-chemical-use categories comprised 42.6%, 39.4%, and 17.9%, respectively, of total person-years of employment. Cumulative exposure scores were also developed, representing a relative measure of the cumulative extent of potential exposure to the six chemical agents, six chemical classes, and general (including unspecified) chemicals. Additionally, the study period was divided into manufacturing eras showing trends in chemical use, and showing that process use of trichloroethylene and methylene chloride ended in the mid-1980s and the mid-1990s, respectively. This approach may be useful in other assessments addressing a variety of chemicals, and with data constraints common to retrospective chemical exposure studies.

Environmental surveillance at Los Alamos: an independent reassessment of historical data

Since 1971, a series of annual Environmental Surveillance ... reports have served as the official public record of Los Alamos National Laboratory's (LANL) environmental performance. In northern New Mexico, where past LANL emissions are a public health concern, there is public skepticism over the accuracy of information contained in these reports. To test the hypothesis that LANL Environmental Surveillance ... reports systematically understate past emissions, we compared the data on releases in LANL's own internal Occurrence Reports Collection (ORC) to the data reported to the public in the Environmental Surveillance ... reports. A data set of 89 environmental occurrences recorded in the ORC in the time period from 1971 through 1980 was assembled. We did not find a systematic pattern of quantitative underreporting of source terms. However, 17 of the 89 (19%) environmental occurrences recorded in the ORC were not reported to the public in the Environmental Surveillance ... reports. The observed discrepancies are discussed in terms of their relevance to public health concerns. Methodological caveats dictate restraint in applying these findings beyond the scope of the relative comparison performed here. Possible social origins for the rejected hypothesis are discussed. Areas for further consideration by the Centers for Disease Control's dose reconstruction study of LANL are identified.

On the use of different measures of exposure-experiences from a case-control study on testicular cancer and PVC exposure

Associations between exposure to PVC plastics and testicular cancer have been reported. To improve the exposure-response analysis in a matched case-control study on testicular cancer and occupational exposures, a self-administered exposure questionnaire and expert assessment was applied and different exposure measures were developed. The questionnaires regarding work histories and employment in PVC production, manufacturing, and handling of PVC products were completed by 1582 subjects (90%). By expert assessment, 360 subjects were considered exposed, and the exposure intensity to PVC plastics for different working periods was determined. Different exposure measures to PVC plastics were then developed, such as ever/never exposed, duration, maximum intensity, median intensity, and cumulative median intensity. The correlation between the different measures of exposure was high for exposure duration and the cumulative median exposure intensity (Spearman rank coefficient r(s) = 0.94), as was the correlation between the maximum intensity and the median intensity (r(s) = 0.94). The agreement between the answers in the questionnaire and the expert assessments was moderate, Kappa value 0.56. The odds ratio for "ever" exposed based on the exposure as reported in the questionnaire was 1.1 (95%, CI 0.82-1.56), and as determined by expert assessment 1.3 (CI 1.05-1.69). The odds ratios for all four different categories of exposure measures varied between 0.86 and 2.6 but decreased by increasing exposure. An overall excess of testicular cancer for the PVC exposed vs. the unexposed was not supported by the pattern seen in a standard exposure-response analysis based on several exposure measures. The findings stress the importance of using several exposure measures as dose surrogates when the underlying toxic mechanisms are unknown and when there are indications of an overall effect.

Laboratory probing of oncogenes from human liquid and solid specimens as markers of exposure to toxicants

Recent discoveries regarding the mechanistic role of oncogenes and tumor suppressor genes in cancer development have opened a new era of molecular diagnosis. It has been observed repeatedly that genetic lesions serve as tumor markers in a broad variety of human cancers. The ras gene family, consisting of three related genes, H-ras, K-ras, and N-ras, acquires transforming activity through amplification or mutation in many tissues. If not all, then most types of human malignancies have been found to contain an altered ras gene. Because the ras oncogenes actively participate in both early and intermediate stages of cancer, several highly specific and sensitive approaches have been introduced to detect these genetic alterations as biomarkers of exposure to carcinogens. There is also mounting evidence that implicate chemical-specific alterations of the p53 tumor suppressor gene detected in most human tumors. Therefore, it seems a reliable laboratory approach to identify both altered p53 and ras genes as biomarkers of human chronic or intermittent exposure to toxicants in a variety of occupational settings.