Toward Chemical Integrity:
The Challenge of Contaminated Sediment and Human Health Impacts
For people in the region, the Great Lakes have long been an
abundant source of food, in the form of fish. In 1990, the International Joint
Commission concluded there was a risk of injury from persistent toxic
pollutants that had found their way through the ecosystem into the tissues of fish.
Based on a growing volume of research, the Commission expressed
particular concern about the effects of these substances on children who had
been exposed in the womb, and as infants, to residues of toxic pollutants.
"When available data on fish, birds, reptiles and small mammals are
considered along with this human research, the Commission must conclude that
there is a threat to the health of our children emanating from our exposure
to persistent toxic substances, even at very low ambient levels ... The
mounting evidence cannot be denied. Governments must emphasize development and
implementation of a comprehensive, binational program to lessen the use of,
and human exposure to, persistent toxic substances found in the Great Lakes
environment. These chemicals appear to be causing serious and fundamental physiological
and other impacts on animal populations in the Great Lakes basin, and undoubtedly
elsewhere. The dangers posed to the ecosystem, including humans, by the continuing
use and release of persistent toxic contaminants are severe."1
The Commission's 1990 conclusion, based on the earliest findings of harm
to the health of children of mothers consuming large quantities of Lake
Michigan fish, underscored the fact that scientific studies of the effects of
persistent toxic substances on wildlife could predict effects on humans.
Those studies had accumulated over the course of 30 years, and
consistently showed that exposure to toxic substances in an ecosystem's food chain
likely leads to adverse health effects in fish, reptiles, birds and mammals.
Studies continue. Today, a convincing body of scientific research
clearly links human exposure to toxic substances in the Great Lakes to
serious injury to health. These investigations include both epidemiological
and experimental research studies, undertaken by Canada's former Great
Lakes Health Effects Program and, in the U.S., by the Agency for Toxic
Substances and Disease Registry.
Other relevant findings from this decade of research include:
- numerous health effects observed
in animals have been reported in humans
- concentrations of toxic
polychlorinated biphenyls (PCBs), in the waters of all Great Lakes are
approximately 100 times higher than the Great Lakes Initiative criteria for
the protection of human health4
- the most significant known
human exposure to toxins from the lakes comes from consuming
contaminated Great Lakes fish
- the people at higher risk
include sport and subsistence fish anglers, some ethnic populations,
pregnant women, fetuses, nursing infants, young children, the elderly and
the urban poor5
- there are effects on the
reproductive function, such as conception rates and changes in the menstrual cycle
- maternal consumption of contaminated fish leads to exposure of
the developing embryo and fetus and results in irreversible
neuro-behavioral and developmental deficits after birth; consuming
contaminated fish also affects neurological functioning
- over five million people eat Great Lakes sport
fish.6 Among these are the high risk populations noted above.
In addition to injury to health, there are also economic and social impacts.
The total economic cost to society for dealing with the health effects
from exposure to contaminants has only begun to be estimated. At
present, almost all of those costs are borne by individuals, families and
non-federal institutions. Other costs include declining property values, and impacts
on the tourism and recreation industries. Because navigational dredging
can stir up or re-suspend contaminated sediment, economic harm can result
in the form of added costs to, or restrictions on, the shipping industry.
The inability to accurately estimate such costs under-represents the true harm
to society from the continuing presence of contaminants and undermines
the needed sense of urgency for action.
In short, we now know that injury is occurring. We believe that
agencies' political leaders and managers are obligated to act decisively
to protect their citizens from further injury.
The 1987 Protocol to the Great Lakes Water
Quality Agreement formalized the concept of Remedial
Action Plans for restoring beneficial uses in Areas of
Concern. More than a decade of compelling research documents
subtle but serious injuries to the health of basin
residents from exposure to persistent toxic substances. Yet
Great Lakes ecosystem restoration continues to be delayed
and public health continues to be injured.
While human exposure to persistent toxic substances in the
aquatic environment is an obvious concern, some preliminary data
now suggest that simply living near contaminated sites and/or in
the geographic boundaries of an Area of Concern may also result
in increased rates of illness and mortality beyond those experienced
by the general population elsewhere in that state or
province.2 More study clearly is required before this possibility can be
confirmed. However, the Commission is concerned about this broader
exposure and is engaged in cooperative efforts with its boards, the Agency
for Toxic Substances and Disease Registry, and Health Canada to
further its understanding and will report with more certainty in the future.