In the first national study of dioxin levels in multiple mediums, the Environment Agency found generally average contamination levels, but also a few surprises, the agency said Friday.

The agency studied dioxin levels in seven mediums -- air, incinerator dust, bodies of water (rivers and bays), groundwater, sea life, soil and sediment -- at nearly 400 sites nationwide and found contamination levels mostly in line with prior studies.

However, the study found new highs in aquatic sediments at 260 picograms per gram of sediment, aquatic life at 30 picograms per gram of fat, groundwater at 5.4 picograms per liter and dust near waste incinerators at 170 picograms per cubic meter per day. A picogram is a trillionth of a gram.

Also, five places studied exceeded the national dioxin air quality guideline of less than .8 picograms per cubic meter of air.

Agency officials played down the new highs, saying that they were found in relatively polluted areas, near incinerators or in urban areas, and that with the increased number of samples it is natural to expect some elevated values. They also emphasized that the high values found in fish are species not eaten by people -- carp and dace -- and were taken from urban rivers not used for fishing.

Dioxin concentrations in all mediums decreased with distance from waste incinerators and cities, except for contamination in groundwater, which was found to be generally uniform.

A correlation was found between levels of dioxin in air and dust particles from incinerators, but no other ties -- such as between levels of the chemical in water and in fish -- were found.

As specified under a law passed earlier this year to address dioxin contamination levels in the environment, the study included coplanar polychlorinated biphenyls, inflating dioxin levels on average.

In 80 percent of the samples, PCBs accounted for between a tenth and a third of the dioxin levels, but in aquatic life samples it made up the majority of dioxin contamination in over 70 percent of the samples. PCBs are chemicals similar to dioxin in structure and toxicity.

The study marks the direction for future research and also furnishes the government with material it can use to set standards on dioxin levels in air, water, soil and sediment.

Agency officials say standards will probably be made public around the middle of December.