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Dioxins

Polychlorinated dibenzodioxins (PCDDs), or simply dioxins, are a group of chemical organic compounds which are significant environmental pollutants. Members of the PCDD family have been shown to bioaccumulate in humans and wildlife due to their lipophilic (fat loving) properties, and are known to cause birth defects, mutations, and cancer in humans. The word "dioxins" may also refer to a similar but unrelated compound, the polychlorinated dibenzofurans (PCDFs) of similar environmental significance.

Dioxins are inherently unstable, possessing only a single electron. Dioxins formed during the burning of fuel and wastes are released into the air. Soil near the burn areas also may be contaminated with dioxins. Surface water bodies can become contaminated when rainwater carries dusts containing dioxins into surface water and so too when they permeate into ground water. Some industries discharge their dioxin-contaminated waste directly into surface water. Dioxins are found in soil, surface and ground water, sediment, plants and animal tissue.

They readily attach to particulates and are subject to gravity in air and water. Dioxins last for a very long time in the environment before breaking down. Dioxins do not easily dissolve in water; they tend to settle to the bottom and cling to the sediment. They penetrate sediments where they are consumed by microscopic organisms which nurture the marine food chain. Aerial fall out contaminates growing crops and croplands contaminating human and animal foods. Dioxins are easily absorbed by animals and are stored in fatty tissue.

In humans and animals Dioxins build up primarily in fatty tissues over time (bioaccumulate), so even small exposures may eventually reach dangerous levels. In 1994, the US EPA noted that non-cancer effects (reproduction and sexual development, immune system) may pose an even greater threat to human health. PCDD, the most toxic of the dibenzodioxins, is classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC). PCDD has a half-life of approximately 8 years in humans. The health effects of dioxins are mediated by their action on a cellular receptor, the aryl hydrocarbon receptor (AhR).

Exposure to high levels of dioxins in humans causes a severe form of persistent acne, known as chloroacne. A case control study has shown an elevated risk of sarcoma (a type of cancer) associated with low-level exposure (4.2 fg/m3) to dioxins from incineration of plant material. High levels of exposures to dioxins have been shown by epidemiological studies to lead to an increased risk of tumors at all sites. Most of us receive almost all of our dioxin exposure from the food we eat: specifically from the animal fats associated with eating beef, pork, poultry, fish, milk, dairy products. Most of us get these foods through the commercial food supply. Other effects in humans may include:

  • Developmental abnormalities in the enamel of children' teeth.
  • Central and peripheral nervous system pathology
  • Thyroid disorders
  • Damage to the immune systems
  • Endometriosis
  • Diabetes

Recent studies have shown that exposure to dioxins changes the ratio of male to female births among a population such that more females are born than males.

Dioxins were produced as by-products in the manufacture of organochlorides (now banned in the U.S., since 1977), in the incineration of chlorine-containing substances such as PVC (polyvinyl chloride) with hydrocarbons, in the bleaching of paper, and from natural sources such as volcanoes and forest fires. There have been many incidents of dioxin pollution resulting from industrial emissions and accidents; the earliest such incidents were in the mid 19th century during the Industrial Revolution.

Dioxins can be commonly detected in air, soil, sediments and food. Dioxins are transported primarily through the air and are deposited on the surfaces of soil, buildings and pavement, water bodies, and the leaves of plants. Most dioxins are introduced to the environment through the air as trace products of combustion. The principal route by which dioxins are introduced to most rivers, streams and lakes is soil erosion and storm water runoff from urban areas. Industrial discharges can significantly elevate water concentrations near the point of discharge to rivers and streams. Major contributors of dioxin to the environment include:

  • Incineration of Municipal Solid Waste and Medical Waste
  • Secondary Copper Smelting
  • Forest Fires
  • Land Application of Sewage Sludge
  • Cement Kilns
  • Coal fired and biomass fueled Electricity Power Plants
  • Residential Wood Burning
  • Chlorine Bleaching of Wood Pulp
  • Backyard burning of household waste
  • Volcanic ash eruptions
  • Exhaust from vehicles

Dioxin was the primary toxic component of Agent Orange, was found at Love Canal in Niagara Falls, NY and was the basis for evacuations at Times Beach, MO and Seveso, Italy.

A recent study by the U.S Environmental Protection Agency found that the amount of cancer causing dioxin and furan emissions from 15 households burning trash each day is the same as those emissions from a 200 ton per day municipal waste incinerator with high efficiency emission control technology.

"Burning any material, whether plastic, paper or wood, produces a variety of hazardous and toxic air pollutants, including carcinogens such as arsenic, benzene and formaldehyde. Children and others with asthma are especially at risk from smoke from burning garbage," said Jim Zellmer, of the Department of Natural Resources waste and materials management program. "If you burn trash, you're affecting your health and the environment more than you know. Where there's smoke, there's pollution – and other risks."

Because of its environmental risk, burning trash in Wisconsin is illegal. In addition, Wisconsin's recycling law and local ordinances prohibit landfilling or burning recyclable materials. Agricultural and horticultural plastics like silage film, haylage bags, bale wrap, woven tarps, nursery pots, and trays must also be recycled or landfilled. It is also illegal to burn plastics in Wisconsin. Materials that are not recyclable should go to a legal disposal facility, not a burn barrel or pile.

Materials that are legal to burn, such as leaves and brush, are regulated under state code. Burning permits are required for debris burns and only authorize the burning of legal materials.

More information on how to handle waste materials is available on the DNR website.

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