After nearly 30 years, the EPA could finally put a limit on the amount of these cancer-causing chemicals we should be exposed to every day.

The food and chemical industries are lobbying hard against what is expected to be a tough report from the Environmental Protection Agency (EPA). The report will set an upper limit for safe consumption of dioxins.

Most Americans consume dioxins at levels higher than this standard, mostly from food. About 90 percent of dioxins come from foods, particularly high-fat animal foods.

Dioxins mainly enter the food chain as by-products of industrial processes. To a lesser extent, they also come from natural processes such as volcanoes and forest fires. They contaminate land and sea, are consumed in feed, move up the food chain, and end up in the fatty parts of meat, dairy products, and seafood.

Dioxins accumulate in fatty tissues. They increase the risk of human cancer more than any other industrial chemical.

The EPA is expected to recommend an intake limit of 0.7 picograms of dioxin per kilogram body weight per day. A picogram is one trillionth of a gram. The World Health Organization and European Union limit is higher -- from one to four picograms per kilogram per day.