Plastics: a new toxic time bomb?

Posted: 17 February 2011

The  need for more intensified research on the impact of plastics entering the oceans is highlighted in the newly published UN Environment Programme's 2011 Year Book.

Scientists are becoming concerned not only about the direct damage to wildlife, but the potential toxicity of some kinds of materials called microplastics.

These are tiny pieces smaller than five millimeters in length discharged as pellets by industry or formed as a result of bigger pieces of plastic broken down by, for example, wave action and sunlight.

The exact quantities of plastics, including microplastics entering or forming in the oceans from the land-based discharge-but also from shipping and fishing boats- is unknown.

What is known is that per capita consumption of plastics, from packaging to plastic bags and from industry to consumer goods, has been rising sharply.

In North America and Western Europe each person now uses around 100kg of plastic materials annually-this is likely to increase to 140kg by 2015.

People in rapidly developing countries in Asia each use around 20kg of plastic per year-this is set to grow to about 36kg by 2015.

Currently recycling and re-use rates vary enormously even among developed countries.

In Europe recycling rates of plastics for energy generation ranged from 25 per cent or less in several European countries to over 80 per cent in Norway and Switzerland.

Previous concerns about plastics included damage and death of wildlife after becoming entangled.  

There is also concern about wildlife eating plastics often in mistake for food.  Albatrosses, for example, may mistake red plastic for squid, similarly turtles confuse plastic bags for jellyfish. Young sea birds of some species may suffer poor nutrition if they feed on too much plastic, mistaken as food.

Persistent toxics

But the Year Book flags a new and emerging concern termed "persistent, bio-accumulating and toxic substances" associated with plastic marine waste.

Research indicates that the small and tiny pieces of plastic are adsorbing and concentrating from the seawater and sediments a wide range of chemicals from polychlorinated biphenols (PCBs) to the pesticide DDT.

"Many of these pollutants including PCBs cause chronic effects such as endocrine disruption, mutagenicity and carcinogenicity," reports the Year Book.

"Some scientists are concerned that these persistent contaminants could eventually end up in the food chain, although there is great uncertainty about the degree to which this poses a threat to human health and ecosystem health," it adds.

Species such as swordfish and seals-which are at the top of the food chain-are cited as potentially vulnerable. These are also species consumed by humans.

A recent survey of PCB concentrations in pellets washed ashore has been carried out at 56 beaches in nearly 30 countries.

Plastic pellets 

The highest concentrations were found in plastic pellets in the United States, Western Europe and Japan-the lowest in tropical Asia and southern Africa

The Year Book chronicles a range of existing and new initiatives, guidelines and laws aimed at reducing plastic and other waste discharges.

These range from the UN's International Convention for the Prevention of Pollution from Ships to UNEP's Global Programme of Action for the Protection of the Marine Environment from Land-based Activities.

The Year Book calls for better enforcement of such rules, better consumer awareness and behavioral changes and improved support for national and community-based initiatives.

There is also an urgent need for improved and more innovative monitoring of plastic throughout the marine environment given that real gaps remain in understanding the ultimate fate of these materials.

There is evidence that some plastics are not floating but sinking and piling up on the seabed.

"Plastic debris has been observed on the ocean floor from the depths of the Fram Strait in the North Atlantic to deepwater canyons off the Mediterranean coast-much of the plastic that has entered the North Sea is thought to reside on the seabed," says the Year Book.

It also calls for phasing in changes in the collection, recycling and re-use of plastics. "If plastic is treated as a valuable resource, rather than just a waste product, any opportunities to create a secondary value for the material will provide economic incentives for collection and reprocessing," the Year Book points out.

See also Fertilizers and plastics are poisoning the oceans, says UN

The UNEP Year Book 2011 is available at www.unep.org/yearbook/2011.