July/August 1997
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July/August 1997 |
by Michael Gilbertson
Are contaminated harbor sediments, leaking waste sites and other sources of chemical pollution being cleaned up quickly and fully enough to protect human health? Findings presented at a major U.S. and Canadian health conference in May 1997 suggest that we should consider doing more.
Back in 1909, the International Joint Commission was set up under the Boundary Waters Treaty to help the United States and Canadian governments resolve potential disputes over the use and quality of their shared waters. Under the treaty, both countries agreed not to pollute the boundary waters to the injury of health or property on the other side. When the two countries signed the 1972 Great Lakes Water Quality Agreement, however, they admitted that pollution was causing injury to health and property on the other side.
Significant progress was made in the 1970s to maintain and restore water quality in the Great Lakes basin. Controls on discharges led to rapid declines in the concentrations of long-lasting toxic substances and in the frequency of health problems in wildlife. But, since the late 1970s, this type of basinwide progress has been almost imperceptible.
So, are the persistent toxic substances that remain in the system causing injury to human health? How many people are affected, and is the injury serious enough to warrant more stringent requirements in the United States and Canada under cleanup programs such as the Remedial Action Plans and the Lakewide Management Plans?
During the past ten years, the Canadian, United States and Quebec governments have invested almost 50 million dollars in research on the exposures and effects of Great Lakes pollutants on human health. The scientists involved in this research reported the results of their investigations at the Health Conference '97 -- Great Lakes/St. Lawrence, held May 12-15, 1997 in Montreal, Quebec. The conference was convened by the U.S. Agency for Toxic Substances and Disease Registry, Health Canada and the Quebec Ministry of Health and Social Services.
Major concerns were the effects of Great Lakes persistent toxic substances on human reproduction and development. This research focus had originally been stimulated by observations in wildlife of reproductive failure and deformities in colonies of fish-eating birds in the 1970s. Findings of low birth weight and abnormalities in infants born in communities close to chemical waste dump sites added to the concern.
There are many chemical pollutants that have been found in Great Lakes fish, waterfowl and turtles that are being eaten by many different groups of people. The challenge has been to pinpoint the substances, such as PCBs and dioxins, that have caused the effects. Groups that are particularly at risk include pregnant women and their fetuses, the elderly, natives and the urban poor who depend heavily on Great Lakes fish and wildlife as sources of nutrition. Because these groups are involuntarily exposed or have little access to power, there is a serious issue of environmental justice and equity that should be addressed. A further concern is that the concentrations found in human tissues are close to the levels at which animals are affected in laboratory experiments.
Despite the continuing debate that is characteristic among scientists, there is a growing consensus within the scientific community that the epidemiologists -- scientists who study how disease is distributed throughout a population -- have successfully demonstrated that effects are occurring in the more highly exposed groups. For example, in studies of newborn infants of women who had eaten Lake Michigan or Lake Ontario fish prior to pregnancy, researchers showed changes in behaviour in the groups that were most highly exposed.
The group of infants whose mothers had eaten Lake Michigan fish prior to pregnancy have been assessed for up to 11 years. The most highly exposed group scored on average 6.2 points lower on IQ tests and they were a year behind their peers in school. The implications of these studies are that exposure of the developing embryo and fetus to persistent toxic substances causes irreversible neurobehavioural and cognitive damage. The effects are subtle deficits in the potential development of the individual, particularly to general intellectual ability, memory and attention. While these deficits do not result in clinical harm -- the children would not be diagnosed as mentally retarded -- they do represent significant impairment for the exposed population. In adulthood, for example, the impairment may show up as loss of earning power.
A group of Quebec researchers has shown that adults who eat fish from the St. Lawrence River have poorer results on certain memory and attention tests indicating changes in neurological functioning caused by the pollutants in the fish. Other researchers are investigating the possible relationship between the consumption of Lake Ontario fish and wildlife and the functioning of the immune system in a group of adults in upper New York state.
The challenge for scientists and policy analysts at this time is how to integrate the evidence and present it so that it can be used by decision makers. The weight of evidence concerning the injury to groups of people who are more highly exposed to Great Lakes chemical pollutants has been steadily growing over the past decade. Researchers at the Montreal conference added to this increasing body of knowledge. There are several implications that arise from the new findings.
The first implication is that it takes time for researchers to satisfactorily document the relationship between the exposures to persistent toxic substances from the Great Lakes and the occurrence of effects on the population. The first studies were initiated about 25 years ago. In many ways this situation resembles the development of the science concerning the subtle effects on neurobehavioural and cognitive development of the exposure of infants and children to lead. In both circumstances, social costs of the injury to the exposed populations might have been forestalled with earlier interventions based on the preliminary findings and concerns.
A second implication of the findings concerns whether the fish advisories are effective tools for protecting that part of the population that is depending on fish and wildlife as a source of nutritious food. For example, while fish contain essential fatty acids that improve growth of the developing fetus, the persistent toxic substances associated with Great Lakes fish retard growth in the developing fetus. In addition, women store persistent toxic substances in their fatty tissues and release these substances into their milk during breast feeding. The dilemma posed by these findings is how can the health authorities protect human health in a democracy when people make personal choices that may be against their interests and those of their children?
A third implication is the need to further remediate the contaminated sites around the Great Lakes. Preventing the release of persistent toxic substances from these sites and restoring water quality are the only ways to insure that the food web will not be contaminated and no injury will occur to populations of humans dependent on foods taken from the wild. In addition, there is a continuing need for vigilance in screening new chemicals and chemicals already in use to prevent the kinds of pollution that have led to these toxicological effects.
The Boundary Waters Treaty and the Great Lakes Water Quality Agreement have been used as models by governments in other parts of the world. Similarly, the research program undertaken by the United States, Canadian and Quebec governments to investigate the effects of persistent toxic substances in the Great Lakes and St. Lawrence River on human health is a model for governments in other parts of the world. The challenges are to utilize the new evidence and to prevent future generations of humans from being injured by chemical pollutants.
The International Joint Commission has scheduled a workshop on policy implications to review the findings that were presented at the Montreal conference and to discuss whether the evidence indicates that further policy options should be developed and implemented. The workshop, with invited researchers and policy analysts, will be held at the Wingspread Conference Center, Racine, Wisconsin from September 5-7, 1997 and the results of the workshop will be presented to Commissioners at the public forum to be held November 1-2, 1997 in Niagara Falls, Ontario.
Michael Gilbertson is a biologist with the International Joint Commission. For more information, contact the author at the International Joint Commission, 100 Ouellette Avenue, Windsor, ON N9A 6T3, or International Joint Commission, P.O. Box 32869, Detroit, MI 48232-2869. Fax (519)257-6740; Email gilbertsonm@ijc.wincom.net .
Sommaire
Est-ce que les opérations de nettoyage des sédiments contaminés dans les ports, de lutte contre les rejets à partir de décharges et d'élimination des autres sources de pollution chimique sont assez rapides et assez complètes pour assurer la protection de la santé humaine? Selon les informations présentées à la conférence sur la santé dans le système Grands Lacs/Saint-Laurent (Conférence Santé 97) qui a eu lieu à Montréal, au Québec, du 12 au 15 mai 1997, il faudrait en faire davantage à ce chapitre.
Malgré les débats permanents qui caractérisent la communauté scientifique, de plus en plus de ses membres s'entendent avec les épidémiologistes (qui étudient comment les maladies se propagent dans les populations) pour affirmer que les polluants produisent effectivement des effets chez les groupes les plus exposés.
Ainsi, un groupe de chercheurs du Québec a montré que les adultes qui consomment des poissons du Saint-Laurent obtiennent des résultats moins élevés que les autres à certains tests de mémoire et d'attention, ce qui révèle que les polluants contenus dans ces animaux agissent sur la fonction neurologique. D'autres chercheurs examinent la relation possible entre la consommation de poissons et d'autres espèces sauvages du lac Ontario et le fonctionnement du système immunitaire chez un groupe d'adultes du nord de l'État de New York.
Revised: July 7, 1997
Maintained by Kevin McGunagle,
mcgunaglek@ijc.wincom.net