Human Health and the Ocean

The world's oceans provide great health benefits to humans ranging from food and nutritional resources, to recreational opportunities and new cures for human disease. The increasing human population and migration trends to coastal zones continue to increase pressure on the ocean-land interface. Coastal degradation, climate variability and increased industrialization will heighten the risk of mobilization of anthropogenically derived, and natural toxic agents in the environment and thus their transfer to humans. Presently, it is estimated that 60 percent of the world's population lives in coastal areas. In fact, human population growth in coastal zones is about twice that of global population growth. Worldwide, about 1 billion people rely on fish as their main source of animal protein. Dependence on fish is usually higher in coastal than in inland areas. About 20 percent of the world's population derives at least 20 percent of its animal protein intake from fish, and some small island states depend on fish almost exclusively.

Health threats

Contaminants in the aquatic food chain are threatening all fishing communities that still rely on seafood for their subsistence. The highest body burden of methyl mercury, or organochlorines (OCs) such as DDT and PCBs, has been found in remote maritime populations in the Northern and Southern hemispheres. Recent reports show that highest human concentrations and related health effects were found in children living in the Canadian Arctic and remote Canadian fishing populations. Various biological effects as well as clinical effects have been seen on the immune system and the brain development of exposed children. More recently, these compounds have been found to possess endocrine properties and have been associated in animals and humans with male fertility problems. We do not have exposure data for most parts of the world.
For many centuries, coastal communities had to face the presence of highly dangerous natural marine toxins in their sea food (fish and shellfish). There is some evidence that new toxins are present and that toxic blooms are observed more often in coastal waters. Whether or not these phenomena (poisoning cases and fish kills) are related to global climate change is an important area of research. The long term toxicity of some lipophilic marine toxins is unknown and research activities need to be developed. Different monitoring strategies for water, shellfish and human intoxication should be implemented and evaluated for their respective efficiencies.
Viruses, bacteria and parasites are also harmful agents for humans and could be responsible for large epidemic events such as the cholera outbreak resulting in over 500,000 cases and 5,000 deaths in 18 months in the Americas. All around the world, it is estimated that marine contamination related diseases from bathing and seafood consumption are responsible for more than 3 million disability-adjusted years (based on premature death and years of loss of health life) per year, with an estimated economic impact of US$13 billion (in 2002).
Increasing sea water temperature is suspected to be a contributing factor to this unusual event. Fish, as is true of any other food, can cause health problems and can be contaminated at any stage from the moment of capture until it is eaten. Contamination may occur because pathogenic micro-organisms form part of the normal flora of the fish. Because the detection of pathogens is not currently available, prevention strategies are weak.

Assessing health risks

All these chemical and biological hazards affect maritime human populations and the coastal ecosystem. For all these reasons, maritime populations are the most sensitive and the most affected by these global changes, and will thus provide the best early-warning of degradation in the marine environment. Survival and sustainable development are often closely related to global environmental changes for these human groups.
The key objectives in any assessment of marine environmental health on a regional or global scale are to provide information necessary to ensure the maintenance of biodiversity and the integrity of communities, minimize the loss of species, limit human influences on living resources (including genetic richness), protect critical habitats, and safeguard human health. All of these objectives are vital to ensuring sustainable development of coastal and marine resources.
Linking the health of the ocean with that of mankind is a long term endeavour that will require considerable effort and resources.
Prepared by Eric Dewailly, MD, PhD, Director, Public Health Research Unité, CHUQ-Laval University, 2400 d'Estimauville, Beauport, QC,G1E 7G9, Canada, Tel 1 418 666 7000 ext 2223, Fax 1 418 666 2776, e-mail and Anthony Knap, PhD, Director, Bermuda Biological Station for Research, e-mail:, phone 1 441 297 1880