Cancer risk assessment using blood dioxin levels and daily dietary TEQ intake in general populations of industrial and non-industrial countries.

We previously measured polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in U.S. foods and estimated the daily dioxin toxic equivalent (TEQ) intake to be from 0.3 to 3.0 pg 1-TEQ/kg body weight for adults. These values are similar to values reported in Canada, Germany, England, and the Netherlands. The U.S. Environmental Protection Agency (EPA) Dioxin Reassessment Draft Documents currently propose a cancer risk-specific dose estimate of 0.01 pg TEQ/kg body weight/day (U.S. EPA, 1994). This risk-specific dose estimate represents a lifetime (70 years) dose which results in a plausible upper bound cancer risk of 1 x 10(-6) (the probability of one additional cancer per one million exposed population over a lifetime). The proximate source of almost all dioxin intake in the general population is from food. Using our data for daily dietary dioxin exposure and the EPA's proposed risk specific dose, we estimate that over a lifetime a maximum of 30 to 300 excess cancers per million could result from the ingestion of dioxin containing food products. In the U.S. population of 260 million, a maximum range of 7,800 to 78,000 excess cancers over a lifetime (70 years) or 111 to 1,114 cases/year might be directly linked to dioxin exposure from food. Because these calculations are based on conservative approaches to setting an upper bound, "true" risk is not likely to exceed this value. At present, one-third of all Americans will develop cancer over a lifetime and one in four Americans are likely to die from cancer. For 1995, it was estimated that there would be 1,252,000 new cancer cases in the U.S. From this, we calculate that a maximum between 0.009% and 0.09% (111-1,114 cases/year) of all cancer cases in the U.S. might be directly linked to dioxin intake in food, assuming intakes have remained constant over a lifetime. Previous studies have suggested that as much as 70% of the total cancer risk in humans may be attributable to diet, primarily as a function of caloric and synthetic chemicals in the diet. (NAS, 1996) These figures do not take into account the ingestion of more contaminated food products, other sources of exposure, possible interactions of PCDDs and PCDFs with other chemicals, or increased incidence of cancer from the cancer promoting actions of dioxins. In addition, we reviewed average U.S. general population blood TEQ (ppt, lipid) levels, which reflect body burden, with levels of persons living in less industrialized countries. These data were used to compare the cancer risk of individuals living in the U.S., an industrial country, to those living in selected less industrialized countries. With the assumption that similar populations were being compared, it is estimated that in the non-industrial region of north Vietnam there is one-third the risk of dioxin-related cancer compared with the United States, while Cambodians have a dioxin-related cancer risk that is 14 fold less than the U.S. at this time.