| Exposure to trihalomethanes (THMs), including CHCl3, CHCl 2Br, CHClBr2 and CHBr3, can occur by ingesting tap water containing disinfection by-products (DBPs) formed during water disinfection using chlorine. THMs are also present in meat, dairy products, vegetables, baked goods, beverages and other foods. This research addresses the formation, volatilization and sorption of THMs in foods and beverages, and the exposures and risks of THMs due to ingestion.; Among tested beverages and foods, tea formed the highest THM levels (3--67 mug/L). In tea, CHCl3 formation increased with free chlorine concentration, decreased with tea concentration, and was unaffected by steeping time. Experiments designed to portray storage, pouring and serving of tap water and tea showed volatilization losses of THMs up to 90% for water and slightly less for tea, depending on water temperature and standing time.; The adsorption of THMs on foods was tested at 25 and 90 C for a variety of foods. THM uptake depended on food type, preparation and concentration, temperature, and THM species and concentration. Screening tests yielded concentrations from 55--872 ng/g for cauliflower, tomato, mushroom, pepper, spinach, lettuce, celery and broccoli at 25 C, and from 32--1793 ng/g at 90 C for beans, carrots, corn, lima bean, cabbage, tomato, squash, potato, rice, chicken and beef. These concentrations are high relative to those in the literature because volatilization was excluded, foods were cut into small pieces, and initial THM concentrations were high. A plane sheet diffusion model matched experimental results for lettuce and spinach, and a spherical diffusion model matched results for tomato, potato and beef.; Formation and volatilization processes were incorporated into an exposure assessment, after which cancer and non-cancer risks were evaluated. CHCl 3 and CHCl2Br risks from food and beverage ingestion were 3.7 and 0.4 times, respectively, higher than the risk resulting from tap water ingestion alone. Excess lifetime cancer risks from all ingestion sources for CHCl3, CHCl2Br, CHClBr2, and CHBr3 were 8.6, 7.7 and 2.3 and 0.32 x 10-6, respectively. Non-cancer risks, expressed as hazard quotients, were small. These results indicate the need to incorporate THM exposures from beverages and foods into epidemiological and risk studies. |
