Category Archives: POLUTION CONTROL

Dioxins

Definition:
Dioxins  are a group of organic polyhalogenated compounds that are significant because they act as environmental pollutants. They are commonly referred to as dioxins for simplicity in scientific publications because every PCDD molecule contains a dioxin skeletal structure. Typically, the p-dioxin skeleton is at the core of a PCDD molecule, giving the molecule a dibenzo-p-dioxin ring system. Members of the PCDD family have been shown to bioaccumulate in humans and wildlife due to their lipophilic properties, and are known teratogens, mutagens, and confirmed (avered) human carcinogens. They are organic compounds.

Dioxins are found just about everywhere – they are present in the atmosphere, soil, rivers and the food chain. They occur naturally as a result of incomplete burning of organic materials during natural events such as volcanoes and forest fires.

But they are also produced during many man-made events which involve combustion such as waste incineration and in chemical and fertiliser manufacturing plants. They may, for example, be produced during chlorine-based bleaching processes in paper mills, or during the manufacture of herbicides. They are also found in low levels in cigarette smoke and vehicle exhaust fumes.

The introduction of a new chlorine production technique in 1900 meant that they became more widespread. However, in recent years manufacturing and environmental controls have reduced the production of dioxins, and the main source now is the burning of fossil fuels and incineration processes. But because of their potential toxicity, exposure even at low levels, remains a concern.

In living organisms, toxic chemicals are often taken up and stored by fat. This means they can persist in the food chain through a process called bioaccumulation.

They are mainly found in meat and dairy produce, but are also found in poultry, fish and on unwashed fruit and vegetables:

•Fish accumulate dioxins through exposure to water – dioxins are repelled by the water and attach themselves to the fatty fish.
•Unless – as was the case in Belgium – feed becomes contaminated, animals are usually exposed to dioxins in the air settling on their food. They accumulate in the fatty tissue of animals, and the longer that animal lives, the greater the build up.
•Dioxins in the air also land on fruit and vegetables, but washing can get rid of these – they are not absorbed into the plant itself.

Risk Factors:
Environmental campaign groups describe dioxins as among the most dangerous toxins known. Scientists are working to establish their exact toxicity, but a draft report from the US Environmental Protection Agency indicates dioxins are considered a serious threat to public health.

The health risks depend on several factors, including the level of exposure and the particular form of dioxin. For most people, levels in the general environment are not high enough to cause an immediate reaction but over a longer period, potential risks to health include:

•Damage to the immune and reproductive system (with lowering of the sperm count).
•An increased incidence of diabetes.
•A significant increase in the risk of cancer.
Exposure to high concentrations of especially toxic dioxins can cause an acne-like condition known as chloracne which mainly affects the face and upper body, which may last several years after exposure. Chloracne is difficult to cure and can be disfiguring. Other problems include:

•Discolouration of the skin.
•Rashes and redness.
•Vomiting.
•Diarrhoea.
•Lung infections.
•Damage to the nervous systems.
Most concerns now lie with the potential of dioxins to cause cancer. A peer-reviewed study of the population of Seveso (where an explosion in a chemical manufacturing plant in 1976 liberated large quantities of dioxins into the environment) found that, in the ten years following the accident both men and women more likely to have cancer, especially of the blood and lymph tissue, as well as breast cancer.

In 1997, a World Health Organisation group declared the most toxic dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin, or TCDD) a class 1 carcinogen, meaning it causes cancer in humans.

Also of concern is the effect dioxins can have on unborn children and infants, as they can be passed through the placenta or carried in breast milk although the World Health Organisation emphasise that the benefits of breast feeding far outweigh any risks to the baby and child.

While governments and environmental bodies strive to minimise the risk, it’s important to keep in mind that it’s very unlikely that most people in the general population will be exposed to a level of dioxins high enough to cause significant toxic effects.

Resources:
http://www.bbc.co.uk/health/physical_health/conditions/dioxins.shtml
http://en.wikipedia.org/wiki/Polychlorinated_dibenzodioxins

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Plastic Recycling Symbols

The Daily Green offers this handy guide on the various types of plastic:

Number 1 Plastics — PET or PETE (polyethylene terephthalate)

* Found In: Soft drinks, water and beer bottles; mouthwash bottles; peanut butter containers; salad dressing and vegetable oil containers; ovenable food trays.
* Recycling: Pick up through most curbside recycling programs.
* Recycled Into: Polar fleece, fiber, tote bags, furniture, carpet, paneling, straps, (occasionally) new containers

It poses low risk of leaching breakdown products. Recycling rates remain relatively low (around 20 percent), though the material is in high demand by remanufacturers.

Number 2 Plastics

HDPE (high density polyethylene)

* Found In: Milk jugs, juice bottles; bleach, detergent and household cleaner bottles; shampoo bottles; some trash and shopping bags; motor oil bottles; butter and yogurt tubs; cereal box liners
* Recycling: Pick up through most curbside recycling programs, although some only allow those containers with necks.
* Recycled Into: Laundry detergent bottles, oil bottles, pens, recycling containers, floor tile, drainage pipe, lumber, benches, doghouses, picnic tables, fencing

HDPE carries low risk of leaching and is readily recyclable into many goods.

Number 3 Plastics –
– V (Vinyl) or PVC

* Found In: Window cleaner and detergent bottles, shampoo bottles, cooking oil bottles, clear food packaging, wire jacketing, medical equipment, siding, windows, piping
* Recycling: Rarely recycled; accepted by some plastic lumber makers.
* Recycled Into: Decks, paneling, mudflaps, roadway gutters, flooring, cables, speed bumps, mats

PVC contains chlorine, so its manufacture can release highly dangerous dioxins. If you must cook with PVC, don’t let the plastic touch food. Never burn PVC, because it releases toxins.

Number 4 Plastics
LDPE (low density polyethylene)

* Found In: Squeezable bottles; bread, frozen food, dry cleaning and shopping bags; tote bags; clothing; furniture; carpet
* Recycling: LDPE is not often recycled through curbside programs, but some communities will accept it. Plastic shopping bags can be returned to many stores for recycling.
* Recycled Into: Trash can liners and cans, compost bins, shipping envelopes, paneling, lumber, landscaping ties, floor tile

Historically, LDPE has not been accepted through most American curbside recycling programs, but more and more communities are starting to accept it.

Number 5 Plastics –
– PP (polypropylene)

* Found In: Some yogurt containers, syrup bottles, ketchup bottles, caps, straws, medicine bottles
* Recycling: Number 5 plastics can be recycled through some curbside programs.
* Recycled Into: Signal lights, battery cables, brooms, brushes, auto battery cases, ice scrapers, landscape borders, bicycle racks, rakes, bins, pallets, trays

Polypropylene has a high melting point, and so is often chosen for containers that must accept hot liquid. It is gradually becoming more accepted by recyclers.

Number 6 Plastics — PS (polystyrene)

* Found In: Disposable plates and cups, meat trays, egg cartons, carry-out containers, aspirin bottles, compact disc cases
* Recycling: Number 6 plastics can be recycled through some curbside programs.
* Recycled Into: Insulation, light switch plates, egg cartons, vents, rulers, foam packing, carry-out containers

Polystyrene can be made into rigid or foam products — in the latter case it is popularly known as the trademark Styrofoam. Evidence suggests polystyrene can leach potential toxins into foods. The material was long on environmentalists’ hit lists for dispersing widely across the landscape, and for being notoriously difficult to recycle.

Number 7 Plastics — Miscellaneous

* Found In: Three- and five-gallon water bottles, ‘bullet-proof’ materials, sunglasses, DVDs, iPod and computer cases, signs and displays, certain food containers, nylon
* Recycling: Number 7 plastics have traditionally not been recycled, though some curbside programs now take them.
* Recycled Into: Plastic lumber, custom-made products

A wide variety of plastic resins that don’t fit into the previous categories are lumped into number 7. A few are even made from plants (polyactide) and are compostable. Polycarbonate is number 7, and is the hard plastic that has parents worried these days, after studies have shown it can leach potential hormone disruptors.

Sources: The Daily Green March 31, 2008

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