Serum dioxin levels in Seveso, Italy, population in 1976.

On July 10, 1976, an explosion at a chemical plant near Seveso, Italy, released a mixture of chemicals, including 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,4,5-trichlorophenol. As a result, several thousand people in the Seveso area may have been exposed to those chemicals. At that time, human exposure assessment was based primarily on soil levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin. Medical examinations of this potentially exposed population and control subjects were begun in 1976 and in some cases continued until 1985. In 1988, we began assessing human exposure in this population by measuring 2,3,7,8-tetrachlorodibenzo-p-dioxin in small volumes of serum specimens remaining from the medical examinations. As expected, we found that the median serum dioxin levels were highest among people who lived closest to the explosion and were progressively lower among groups living farther away. These measurements have allowed us to assess exposure more accurately among individuals in this population and to relate exposure to various health effects. We found that some individuals in the exposed population had among the highest serum dioxin levels ever reported, yet chloracne was the only unequivocal effect found; cancer risks are still being investigated. We also found that other individuals with as high or higher serum dioxin levels did not develop chloracne. We also found that the serum half-life of dioxin in this population was 7-8 years, which agrees with other findings although we do report some differences in the serum half-life of TCDD for women and children. We also observed an increase in the percentage of female newborns to parents who resided in Zone A at the time of the explosion, and we also report on the 1976 serum dioxin levels in people who later developed cancer.