Selasa, 18 Disember 2012

Pencemaran Plastik Nano

Microplastics From Synthetic Clothing and Plastic in the Environment

Plastics are very useful and popular materials, but they may be dangerous to animals and humans while they are being used or when they are discarded. Chemical additives leached from plastic containers, such as Bisphenol A, may disrupt our hormonal systems, harm our reproductive systems and perhaps increase the risk of cancer. Animals can become trapped in large pieces of plastic garbage, and both large and small pieces may enter their bodies, physically or chemically injuring or killing them. Plastics are widespread in our lives and in the environment, and are sometimes present in unexpected places.

People who refuse to buy plastic or who reuse plastic items if they do enter their home should certainly be encouraged, but they may be shocked to learn that they are probably still adding plastic material to the environment. Researchers have discovered that every time clothing made from synthetic plastic fibers is washed, tiny strands of the garments are removed in the washing machine and may ultimately enter the ocean. Polyester, acrylic and nylon are examples of plastics used to make clothing. One garment can release 1900 plastic microfibers per wash. The fibers form an important part of the “microplastic” present in the ocean. Plastic from other sources slowly degrades to contribute to the microplastic material as well. In addition, very tiny nanoplastic particles are present in many cosmetics and contribute to the plastic collection in the oceans and its sediments.

The Problem With Microplastics

What is Plastic?

Plastic is a synthetic or semi-synthetic material which is molded and shaped when soft and then solidified. Plastics are made of organic polymers. A polymer is a long molecule made of repeating units, and the term “organic” means that the units contain carbon. Plastics can be made from a wide range of chemicals, including polystyrene, polyvinyl chloride (PVC), polyamide (nylon), polyethylene, polypropylene and polycarbonate. One form of acrylic is poly(methyl methacrylate), or PMMA. Acrylics and polyesters are families of plastics.

It’s often thought that plastics don’t degrade, but they do in fact break down, although generally very slowly. (There are some degradable plastics that break up faster than normal plastics.) The long polymers that make up the structure of a plastic gradually break up into shorter and shorter polymers. These degradation products may still be dangerous to living things, however.

In addition, additives used to make the plastic are released as the plastic degrades. These additives include potentially harmful substances such as bisphenol A (or BPA), which is used to make polycarbonate plastics and epoxy resins, and phthalates, which are added to certain plastics to make them pliable and are also present in some cosmetics. Both of these substances are endocrine (hormone) disruptors, but whether or not low levels of the chemicals harm adult humans is a controversial topic. However, many researchers agree that the chemicals are dangerous for a fetus, young children and some animals.

How Do Microplastics Differ From Plastics?

Plastics are classified according to their size. Microplastics are plastic particles less than 5 mm in size (or less than 1 mm in size in some classification schemes). Nanoplastic particles are even smaller and are used in many personal care products. These end up in the water when we wash our skin or brush our teeth. (Many toothpastes contain plastics in the form of polyethylene glycol, or PEG.) Plastics are so ubiquitous in our environment that it's hard for someone to avoid absolutely all sources. A common method of classifying plastics is shown in the table below.

Plastic Classification
> 100 mm
100 mm to 5 mm
5 mm to 0.330 mm
< 0.330 mm

The Great Pacific Garbage Patch

The Great Pacific Garbage Patch is a huge, swirling mass of plastic and microplastic material trapped in a gyre in the North Pacific Ocean and is known as the largest landfill in the world. It's made of two areas called the Western Garbage Patch and the Eastern Garbage Patch. The Eastern Garbage Patch is larger, and its name is sometimes used as a synonym for "Great Pacific Garbage Patch".

The Eastern Garbage patch is very large, but its size is hard to measure and seems to vary. It's been described as being equal to the size of Texas, equal to twice the size of Texas or even equal to the size of Europe. The large pieces of plastic debris in the region are very obvious, although they don't form a continuous cover over the water as some people imagine. This is why the garbage patch can't be seen in satellite photos. Most people are unaware that there is a large quantity of hidden microplastic material in the area. The Great Pacific Garbage Patch is shameful evidence of our love of plastic and our carelessness about its fate and its effect on other creatures when it's no longer useful.

Potential Dangers of Microplastics

The harm caused by large pieces of plastic debris that enter the ocean is well known. Animals may become entangled in the plastic or may mistake it for food. The swallowed plastic may block the animals' intestines, starve them or suffocate them. It may fill their stomachs and take the place of real food. The effects of microplastics on living things are uncertain, but researchers are concerned about their potential influence on the health of marine organisms and perhaps even on us.

Scientists know that microplastics are accumulating in oceans around the world and in ocean sediments, that they take a long time to degrade completely and that they are being ingested by marine animals at the bottom of the food chain. They have also appeared in the bodies of fish. Researchers know that other pollutants stick to the pieces of microplastic and are ingested along with the plastic particles. These pollutants include dioxins, DDT and PCB molecules (polychlorinated biphenyls). The plastic particles might be harmful, but investigators need to demonstrate this in their research.

So much microplastic material is accumulating in the ocean and it's made of such tiny particles that if we do prove that the microplastic is hurting animals - or us - it will be very hard to remove it. It's far easier to prevent the buildup of microplastic (and nanoplastic) material than to remove it.

Studying microplastic is a new endeavor and there's much that scientists don't yet know about this form of plastic. Do the plastic particles hurt living things? Do the pollutants that they carry harm animals? Do the plastic particles and the pollutants become more concentrated as they move up the food chain? Do they affect us when we eat marine animals? These are important questions which still need to be answered.


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