Extrapolations from animal toxicity experiments (including carcinogenicity and reproductive effects) to possible human heath effects can be used to estimate a reasonable level of risk for 2,3,7,8-tetrachlorodibenzodioxin (2,3,7,8-TCDD). Extrapolations are derived from: (1) review of published studies, (2) a complex set of assumptions related to human exposure to contaminated soil, and (3) estimates of (a) a dose response curve, (b) appropriate margins of safety, and/or (c) applicable mechanisms of action. One ppb of 2,3,7,8-TCDD in soil is a reasonable level at which to begin consideration of action to limit human exposure for contaminated soil.

The hypothesis of vitamin A intake deficiencies serving as an antecedent factor in the development of stomach cancer was assessed employing a case-control design. Interviews of proxy informants for 111 cases and a pair-matched control group were conducted using a food frequency questionnaire from which an averaged vitamin A intake index was calculated. Stomach cancer cases showed a significantly higher proportion with lowered total vitamin A intake levels (odds ratio = 1.71) which remained constant across sex and socioeconomic status groupings. These results demonstrated a consistency with previous related studies vis-à-vis the strength and specificity of the putative association, a moderate (but statistically nonsignificant) dose-response curve, proper temporal association, and biologic plausibility.

Historically coal mining populations have been reported to have elevated stomach cancer incidence rates. To identify which factors might be associated with cases who reside in these high risk areas, and specifically if particulate exposures from coal mining and coal utilization are associated with risk, a mining area of western Pennsylvania was defined for a retrospective case-control study. One hundred seventy-eight resident cases, identified from certificates of death, were compared to three controls: digestive cancer deaths, arteriosclerotic heart disease deaths, and neighborhood (living) controls. Controls were matched to each case on age, race, sex, and residence. Interviews were conducted during 1981 and 1982. Excess risks were shown for foreign born and eastern Europeans. Coal mining was not shown to be a risk factor for males, while an association was seen for female cases whose husbands were miners. Farming was a risk factor for males and females. Marked decreased risks were shown for gas heating and cooking fuels, with elevated risks for coal, wood and oil heating fuels, and wood cooking fuel. These findings are associated with lower socioeconomic status, and suggest environmental exposures or lifestyles that are directly and indirectly related to these risks factors. The marked inverse relationship between stomach cancer and use of gas heating and cooking fuel may be of important etiologic significance, especially in association with dietary changes. Further evaluation of prior use of various types of heating and cooking fuels needs to be considered especially using incident rather than case deaths.