New evidence shows that marine animals can take up the toxic chemicals that can become concentrated in small plastic particles

Environmental Science & Technology
November 5, 2008

WHY SMALL PLASTIC PARTICLES MAY POSE A BIG PROBLEM IN THE OCEANS

By Kellyn Betts

Over the past few years, scientists have begun to realize that the
increasing volume of plastic materials slowly decomposing in the
world's oceans may present a long-term problem for marine food chains
already reeling from overfishing and other anthropogenic insults.
Partly as a result of a pair of influential papers published in ES&T,
scientists are now exploring the role that fragments of plastic trash
may play in transporting marine pollutants.

The first international conference about this newly emerging
"microplastics" problem was held in September and sponsored by the
U.S. National Oceanic and Atmospheric Administration (NOAA). Attendees
from six countries agreed to define microplastics as plastic pieces or
fragments smaller than 5 millimeters. Sources of microplastics include
both the small plastic particles used in products like containers for
body washes and cosmetics and the weathering of larger plastic flotsam
and jetsam, says conference organizer Joel Baker of the University of
Washington Tacoma, where the event was held.

Larger plastic debris tends mainly to float on the surface, but
microplastics also can be found in the water column and on the seabed,
says Richard Thompson, a researcher at Plymouth University (U.K) and a
coauthor of both ES&T papers. "This distribution, together with the
smaller size, means that a wider variety of organisms could be exposed
to [microplastics]," he says. Thompson has been at the forefront of
developing methods to definitively identify plastic fragments as small
as 20 micrometers.

As plastic items break down, any toxic additives they contain --
including flame retardants, antimicrobials, and plasticizers -- may be
released into the ocean environment, Thompson explains. Plastics can
act like sponges to collect hydrophobic persistent organic pollutants,
such as PCBs, adds Holly Bamford, director of NOAA's Marine Debris
Program. Microplastic particles have been shown to hold concentrations
of PCBs more than 1 million times higher than those in the surrounding
water, Baker says.

At the recent conference, Hideshige Takada of the Tokyo University of
Agriculture and Technology presented persuasive data that
microplastics can impact marine food chains; the results came from a
feeding experiment with streaked shearwaters, a common seabird in
Japan and Australia. Takada's group, which has analyzed plastic
pellets found on beaches around the world, fed chicks living in their
natural environment a diet of fish laced with PCB-laden polyethylene
resin pellets collected from Tokyo Bay. The pellet-consuming chicks
took in up to 3 times the concentrations of lighter-weight PCB
compounds, or congeners, as did chicks fed fish alone, he reported.

Takada's research buttresses laboratory data published in the ES&T
papers. The first paper (Environ. Sci. Technol. 2007, 41, 7759-7764)
used modeling experiments to show that common marine lugworms can
accumulate phenanthrene, a persistent anthropogenic compound commonly
found in the ocean, when microplastic particles saturated with a small
amount of the contaminant are added to the sediments where the worms
dwell. The second paper (Environ. Sci. Technol. 2008, 42, 5026-5031)
confirmed that captive Mytilus edulis mussels fed microplastic
fragments accumulated the plastic bits in their guts. At the September
conference, Thompson and his colleagues reported that their latest
work appears to confirm that contaminants can transfer from plastics
to live lugworms.

Takada is currently investigating whether microplastics are exposing
marine animals to phenolic compounds, including nonylphenol,
octylphenol, and bisphenol A. "Ingestion of marine plastics could be a
direct and important route of phenolic chemicals to higher animals
such as seabirds," he says. Several studies suggest that
biomagnification does not play an important role in the transfer of
such endocrine-disrupting compounds to animals and birds that are
higher up in the food chain, he adds.

The world now uses 230 million pounds of plastic annually, Thompson
says, noting that much of this is "for one-trip packaging that is
thrown out within a year of production, on average." Because the
plastic that enters the ocean tends to fragment, it is likely to
remain in the environment "for hundreds, if not thousands, of years,"
he says.