Validity of empirical models of exposure in asphalt paving

AIMS

To investigate the validity of empirical models of exposure to bitumen fume and benzo(a)pyrene, developed for a historical cohort study of asphalt paving in Western Europe.

METHODS

Validity was evaluated using data from the USA, Italy, and Germany not used to develop the original models. Correlation between observed and predicted exposures was examined. Bias and precision were estimated.

RESULTS

Models were imprecise. Furthermore, predicted bitumen fume exposures tended to be lower (-70%) than concentrations found during paving in the USA. This apparent bias might be attributed to differences between Western European and USA paving practices. Evaluation of the validity of the benzo(a)pyrene exposure model revealed a similar to expected effect of re-paving and a larger than expected effect of tar use. Overall, benzo(a)pyrene models underestimated exposures by 51%.

CONCLUSIONS

Possible bias as a result of underestimation of the impact of coal tar on benzo(a)pyrene exposure levels must be explored in sensitivity analysis of the exposure-response relation. Validation of the models, albeit limited, increased our confidence in their applicability to exposure assessment in the historical cohort study of cancer risk among asphalt workers.

Hypersensitivity reactions and specific antibodies in workers exposed to industrial enzymes at a biotechnology plant

Thirty-six employees who produced industrial enzymes from selected strains of bacteria and fungi were evaluated by epicutaneous threshold testing and enzyme-linked immunosorbent assays (ELISA) for specific IgE and IgG antibodies. The workers complained of 'asthma- and flu-like' symptoms, which generally lessened away from work. The enzymes evaluated were: alpha-amylase (1,4-alpha-d-glucan glucanohydrolase) from Bacillus licheniformis (alpha ABl), B. subtilis formation 1 (alpha A1Bs) and B. subtilis formation 2 (alpha A2Bs); purified alpha-amylase from B. licheniformis (C alpha ABl) and A. oryzae (C alpha AAo); alkaline protease from B. licheniformis (APBl) and purified alkaline protease (CAPBl); amyloglucosidase (1,4-alpha-d-glucan glucohydrolase) from A. niger (AGAn) and purified amyloglucosidase (CAGAn). Statistically significant increases (P > 0.05) in the proportion of workers having positive skin tests to CAPBl, AGAn and CAGAn were found. Significantly elevated (P > 0.05) mean specific IgE results were observed for C alpha AAo CAGAn and AGAn, and elevated (P > 0.05) mean specific IgGs were observed for C alpha AAo, CAGAn, AGAn, alpha A1Bs, alpha AB1 and alpha A2Bs. These results indicate that occupational exposure to some industrial enzymes can cause immediate-onset cutaneous hypersensitivity reactions, pulmonary function deficits and significantly elevated specific antibody levels. Our results are equivocal as to whether work-related respiratory and cutaneous hypersensitivity reactions are antibody mediated, as there was no statistically significant association between these reactions and specific IgE or IgG levels.