Danger in Irish waters

A forthcoming survey on otters may reveal high levels of a chemical harmful to human health in Irish water. By Shay Fennelly

Otters depend on clean water to live and by studying them we can learn about the cleanliness of the water they habitate. In particular otters are susceptible to polychlorinated biphenyls (PCBs), therefore they are good source to assess the levels of it in the water. PCBs are potentially harmful to humans. A failure by the Government to adequately survey the Irish otter population means we have little idea about the levels of PCB contamination here, but a survey due out in 2006 will give us some idea.

The otter is almost extinct in most of Europe, which makes the Irish population particularly important because they can indicate clean water supplies. Otters thrive where the water is clean and uncontaminated by chemicals. If otters have disappeared from an area it is significant because it could point to some serious environmental contamination.

During the late 1950s the otter population underwent a sudden decline in England, Wales and southern Scotland. Dieldrin, a pesticide widely used in agriculture, until it was banned in 1975, is generally held responsible for the decline of otters in the UK. While it is not clear exactly what compounds in the environment pose the greatest danger to otters at present PCBs are one of the main contenders. In 1969, UK industry agreed to a ban on their use after finding PCB lesions on seabirds dying in the Irish Sea. PCBs can only be completely destroyed by high temperature incineration and are already present in the environment and wildlife, albeit in minute concentrations.

How toxic are PCBs to mammals who accumulate them in their bodies? Experiments with laboratory animals have shown a variety of biological effects of PCBs including weight loss, damage to liver and skin, reproductive toxicity, atrophy of the thymus, immunotoxicity, and teratogenicity. In the Baltic Sea, increased levels of PCBs have been associated with changes in the reproductive tract of seals, in some cases leading to sterility and skeletal deformities, from seals feeding on polluted fish. A Dutch study in 1994 found impairment of the immune function in Harbour seals fed on PCB contaminated herring from the Baltic Sea. A US Department of the Interior investigation in 1996 found young male otters from the Columbia River had abnormally small reproductive organs due to several environmental contaminants present in the river, including PCBs. It has been found that high doses of PCBs cause sterility in female otters. The EU Commission has taken the Irish Government to the European Court of Justice for its failure to implement the Habitats Directive to protect Irish wildlife, including otters. Ireland has failed to establish a system of protection or sufficient surveillance of this species. Close monitoring of otters can highlight subtle changes in the environment, which can be significant for human health. In July 2004, the National Parks and Wildlife Service commissioned the Wildlife Ecology Group in Trinity College Dublin to carry out a national survey of otters in the Republic of Ireland – 24 years after the first otter survey in Ireland.

That otter survey was carried out in 1980/1981 by the Vincent Wildlife Trust, a British wildlife charity. Otter signs were located at 91 per cent of sites surveyed, with most on the west coastline. Otter scientist Dr Liam O'Sullivan said that the 1980 survey only recorded otter signs, with no record of population size, densities or age structure undertaken. "The results certainly show that the otter population is widespread but it has not been shown that it is abundant and healthy." Environment Protection Agency (EPA) water surveys show a decline in water quality in our rivers with some 30 per cent of Irish rivers surveyed in 2001- 2003 classed as moderately or slightly polluted. Otters are likely to have declined since the first otter survey.

In 1992 Dr Liam O'Sullivan, UCC, examined 33 otters, finding several animals from Cork city, where domestic and industrial effluents are discharged directly into Cork harbour estuary, were highly contaminated. Fourteen more otters examined in 1993 revealed three otters with PCB levels considered "very high." One from Bantry, in addition to an elevated PCB level in the liver, had a total of fifteen skin lesions, symptoms that may be induced by elevated PCB contamination. The study recommended an ongoing monitoring program for environmental contaminants in otters (1993). Thirteen years on and there is no program in place. In Ireland the ESB is the authority charged with the safe disposal of PCBs because of their use in electrical transformers and the EPA tries to monitor the use of PCBs. Failure to monitor PCBs in otters wastes their benefit as a sentinel for dangers to human health from waters in Ireland.

In addition to their adverse effects on animals, PCBs are also harmful to humans. A long-term study carried out at the University of Düsseldorf, published in December 2001, concluded that 5 per cent of all children have become "highly contaminated". Their mental and motor development may therefore be impaired. The US Journal of Paediatrics in 1984 published the first study to assess the effects of PCB exposure at ordinary dietary levels in the human infant. Infants exposed to PCB through contaminated fish were born lighter in weight, the head circumference was smaller and the gestational age was shorter. This was consistent with Japanese infants exposed who showed growth impairment and cognitive and motor deficits in later infancy. As early as the 1960s, scientists expressed doubts regarding the safety of PCBs. It was found that the absorption of large quantities of PCBs led to acute dermatological problems, damage to the liver, spleen and kidneys, and weakening of the immune system. Switzerland was one of the first countries to introduce a total ban on PCBs in 1986. For many years PCBs were used in large quantities in transformers and capacitors, as well as softening agents in paints, adhesives and sealing materials. It is estimated that about two million tonnes of PCBs were produced worldwide.