Environmentalists warn that chemical contamination is seriously threatening marine mammals

By Environmental News Network staff

(ENN) -- Chemical contamination is linked to disease, reproductive failure and sporadic die-offs among whales, dolphins and porpoises, according to a report from the World Wildlife Fund (WWF).

"Synthetic chemicals are the stealth bombers of the oceans -- able to travel undetected across continents and drop their deadly loads on the most unsuspecting victims," said Ginette Hemley, director of international wildlife policy.

Biologists have been observing sporadic die-offs, diseased and emaciated animals and reduced reproductive success among marine mammals for some time, the WWF says.

Studies of bottlenose and striped dolphins suggest that viral outbreaks may be related to the presence of synthetic chemicals. Troubling findings of clusters of cancers in beluga whales signal long-term immune system weaknesses, according to the group.

However, long-term impacts of toxic pollutants are often difficult to detect, because mother whales transfer chemicals accumulated in their tissue to their offspring during gestation and lactation, the most sensitive period of development.

There is increasing evidence that chemicals can interfere with a whale's ability to develop normally, to breed and to cope with stress and disease.

PCBs among the health threats

The WWF report is taken from a larger scientific study to be released later this year, and stresses the need to develop a clear picture of chemical impacts on whales and other marine mammals.

It details how certain chemicals, known collectively as persistent organic pollutants because they break down extremely slowly in the environment, pose significant health threats to cetaceans and their offspring. They include:

• PCBs, which are carried by large cetaceans in concentrations at or above those linked with significant neurological impairment in humans. Current background levels of PCBs, dioxins and furans in humans have been found to alter thyroid hormone levels and weaken the offspring's immune system. PCBs also have been linked with hearing loss in animal studies, causing great concern among cetacean scientists, because of the unique dependence of cetaceans upon their auditory system for navigation and communication;
• Mercury, which contaminates freshwater and marine mammal tissue, is increasing at a startling rate in some parts of the world. Mercury's effect on the nervous system and intelligence is well documented. Recent findings suggest that the immune systems of some cetaceans, particularly beluga whales, are exceptionally sensitive to mercury;
• Organotin (organic tin) compounds, such as those found in paint used on ships, pose a threat to cetaceans' food base and perhaps directly to their health and reproductive success by interfering with sex organ development. They also attack the thymus gland, suppressing immune function.
• Plastics and plastic components, such as bottles and packaging that until recently were considered inert, are now recognized as having characteristics that make them biologically active. In the laboratory, several of these globally dispersed compounds undermine the development of the reproductive tract in the offspring of pregnant mice fed exceedingly low doses.
• Pesticides, many of which are designed to inhibit photosynthesis, travel thousands of miles in the atmosphere to the Arctic, where they could potentially destroy the food supply of cetaceans by killing algae.

• Funding from International Whaling Commission member governments to study and combat chemical contamination of cetaceans;
• Government support for a global United Nations treaty on persistent organic pollutants (POPs) that would expedite phasing out their production, release and use;
• Establishment of criteria to identify and target additional POPs for phase-out and elimination.