Daily intake from meals, and excretion from feces and sebum of 20 congeners of polychlorinated dibenzo-pdioxin (PCDD), polychlorinated dibenzofuran (PCDF) and coplanar polychlorinated biphenyl (Co-PCB) were analyzed in healthy Japanese men who are considered to be a standard for the Japanese. Daily intake of these congeners was 84.2 ± 12.5 pg toxic equivalent (TEQ) and daily excretion from feces and sebum were 18.3 ± 5.9 and 23. 8 ± 5.6 pg TEQ, respectively, indicating 22% the daily intake of dioxins from meals is excreted from feces and 29% from sebum. 1,2,3,7,8-Pentachlorodibenzo-p-dioxin (1,2,3,7,2,3,4,7,3,4,7, and 3,3′,4,4′,5-pentachlorobiphenyl (3,3′, 4,4′,5-PeCB) were most abundant in TEQ, in meals, feces, sebum and blood. Co-PCBs were most efficiently excreted among three congener groups in TEQ, especially from sebum. Octachlorodibenzo-p-dioxin (OCDD), 2,3,7,3,7, and 3,3′,4,4′-tetrachlorobiphenyl (3,3′,4,4′-TCB) were well absorbed from intestine and excreted at more than 100% of intake, mainly from the sebum. In contrast, 1,2,3,4,7,2,3,4,7,2,3,7,8,2,3,7,8, were excreted at relatively low levels from sebum, although well absorbed from the intestine, and the excretion ratios were lowest among the 20 congeners. It was suggested that 80.5-85.2% TEQ of each congener-group might be absorbed from the intestine, after taking bile excretion into consideration.

The toxicity of 2,3,7,8-tetrachlorodibenzodioxin (TCDD) has been known since 1950s. TCDD is a by-product of herbicide 2,4-dichloroacetophenol (2,4-D) and 2,4,5-trichloroacetophenol (2,4,5-T), but it was first found in fryash of municipal incinerator in 1979 in Japan. In 1998, the survey of municipal incinerators revealed that 105 out of 1,641 produced above the allowed emission level of 80 ng TEQ/m3. Total annual release of dioxins is estimated to be about 5,000 g TEQ in 1997 in Japan. Japanese government started a comprehensive survey for dioxin levels in milk and blood of residents around incinerators, and their health effects. Human effects by dioxin exposures in Western countries were mostly acute and at high level in accidentally and/or occupationally. Health effects of low-dose and long lasting exposure has not been well understood. Certain amount of polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) and polychlorinated biphenyls (PCB) is accumulated in our body. Mother's milk is also contaminated by PCDD/PCDF. Health effects of the polychlorinated chemicals are summarized, and the necessity of regulations and recommendations for making a guideline is discussed in this review.

The aim of this study was to estimate the contributions of dietary n–3 polyunsaturated fatty acid (PUFA), a representative dietary immunosuppressant, to the activity of both alveolar macrophages (AM) and natural killer (NK) cells, and compare them to those of n–6 PUFA. Twelve 5-week-old female Sprague-Dawley rats were divided into two dietary groups, one fed a 10% fat diet for 9 weeks enriched with n–3 PUFA (n–3 diet) and the other an n–6 PUFA (n–6 diet). AM reduced the release of nitric oxide, monocyte chemoattractant protein 1 and tumor necrosis factor α in the rats fed the n–3 diet, compared with rats fed the n–6 diet. NK cell activity was reduced by consumption of the n–3 diet. This study suggests that consumption of n–3 PUFA can ameliorate pulmonary inflammatory disorders which are affected by the reduction of not only proinflammatory cytokines but also chemokine released from AM.

The effect of dietary docosahexaenoic acid (DHA) on T cell states in peripheral blood was investigated. Weanling male C57Bl/6N mice were kept on one of three 10% fat diets containing various amounts of DHA and linoleic acid for 4 weeks. Changing the concentration of dietary DHA did not alter the proportion of T cells expressing CD4 or CD8. However, increasing the concentration of dietary DHA lowered the expression of CD4 and CD8 on the cell surface. The decreased expression of these surface molecules involved in T cell proliferation has serious implications in the role of DHA as an immunosuppressant.