There has been no significant decrease in the quality of sperm nor the weight of Japanese men’s testes over the last two decades, according to the nation’s most comprehensive survey on dioxin levels in humans and wildlife. The survey, conducted by the Environment agency and released Monday, was conducted as a first step in gaining a better understanding of dioxin contamination levels in people and animals. It measured dioxin levels in humans and a variety of wildlife as well as checking the quality of sperm and weight of testes to determine if, as some reports have indicated, there has been any decrease in recent years. The average of testes increased from around 17 grams in 1964 to slightly more than 19 grams in 1980 before settling at about 18 grams since the early 1990s, the survey shows. Dioxin levels in blood, brain, fat, kidney and umbilical cord samples were analyzed and organs with higher fat content were shown to have elevated dioxin levels. Samples from the brain, however, showed extremely low levels — only between 5 percent and 4 percent of the dioxin levels of other samples.

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