Thousands of pollutants are present in our oceans
We selected 14 contaminant classes of particular concern to ocean health. The effects of some of these contaminants on marine biota and food webs are well-known. The effects of others are only beginning to be understood.
Polychlorinated biphenyls (PCBs) are synthetic heat-resistant oils that were used mainly in electrical applications and heavy machinery. Production and new use of PCBs ceased in the 1970s in North America. However, PCBs continue to persist in the environment and pose a risk to ocean health, notably to animals at the top of food webs, such as killer whales.
Dioxins/furans (PCDD/Fs) are unintentional byproducts of combustion and the manufacture of chlorinated substances. Changes to pulp and paper mill operations in Canada and elsewhere have greatly reduced inputs of these harmful chemicals to the oceans. But because of continued incidental by-production, their persistence, and toxicity, they continue to pose a risk to some aquatic organisms.
Polycyclic aromatic hydrocarbons (PAHs) come from both natural and human sources (e.g., combustion, fossil fuel use). Thousands of different PAHs exist; their size and structure determine their persistence and toxicity in the ocean. Oil spills are one source of PAHs that are of particular concern to ocean health.
Polybrominated diphenyl ethers (PBDEs) are synthetic compounds used as flame retardants in manufactured materials. PBDEs are bioaccumulative and toxic to aquatic organisms. Though they are no longer used in Canada, PBDEs are persistent in the environment and continue to pose a risk to ocean health.
Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant globally, used in epoxy and polycarbonate resins. TBBPA is persistent in the environment, bioaccumulative, and poses a potential health risk to aquatic organisms.
Hexabromocyclododecane (HBCD) is a flame retardant used primarily in thermal insulation for the construction industry. In January 2017, HBCD was banned in Canada. However, it is persistent in the environment, bioaccumulative, and it continues to pose a potential health risk to marine life.
Metals – Cadmium
Cadmium is a naturally-occurring trace element and is also produced by human activities (metal smelting and refining, fuel burning, wastewater treatment). Cadmium is readily accumulated by marine organisms, particularly plankton and invertebrates, and can have toxic effects in all organisms if present at high enough levels.
Metals – Lead
Lead is naturally-occurring and is also produced by human activities (coal burning, metal smelting, waste incineration). Lead exposure from ingestion of fishing tackle is known to cause a range of toxic effects in birds. Lead also has toxic effects in marine invertebrates, and can have adverse effects in all organisms if present at high enough levels.
Metals – Mercury
Mercury is naturally-occurring and is also produced by human activities (coal burning, metal smelting, mining). Methyl mercury is the main form absorbed by fish and wildlife. It increases in concentration in the tissues of organisms as it moves up the food chain, posing potential health risks for top marine predators.
Perfluorinated compounds (PFCs) are used to make products more resistant to stains, grease, and water. PFCs are persistent in sediments and bioaccumulate in fish, birds, and marine mammals. PFCs are toxic to aquatic organisms, and key PFCs (PFOS and PFOA) are now strictly regulated in Canada.
Alkylphenols are synthetic compounds used to make alkylphenol ethoxylates (APEs), widely used as surfactants in detergents, degreasers, emulsifiers, wetting agents, and dispersing agents. Nonylphenol and its ethoxylates are dominant in the marine environment. These compounds are endocrine disruptors: they can mimic estrogen and disrupt regular hormone processes.
Organotins are used as pesticides and stabilizers for polyvinyl chloride plastic products. They are also used in antifouling paints to prevent the accumulation of barnacles and other organisms on boat hulls and fishing gear. Tributyltin is one of the most toxic organotins, affecting hormone and immune system functions. Its use in anti-fouling paints was banned in Canada in 2002.
Legacy pesticides are organochlorine pesticides that were banned or restricted in the 1970s and 1980s in North America and many other countries. Their legacy is that they persist in the environment long after their use. They are soluble in lipids, accumulating in the fatty tissues of organisms, and have a range of toxic effects in marine biota. DDT is considered one of the most notorious legacy pesticides, having been associated with eggshell thinning in aquatic birds in the 1960s and 70s.
Current Use Pesticides
Current use pesticides (CUPs) are a diverse group of chemicals currently used in Canada and around the world. CUPs are generally more target-specific and less persistent than legacy pesticides, but some are more acutely toxic. Many are water soluble, meaning that they move easily in aquatic environments. CUPs have a range of toxic effects based on their mode of action, and are often toxic to non-target organisms.
Pharmaceuticals and personal care products (PPCPs) include all medications made for humans and animals, as well as cosmetics, soaps, lotions, and hair and dental care products. While some PPCPs degrade quickly, others persist in the environment and are known to accumulate in aquatic organisms. PPCPs can have a variety of toxic effects in biota, and the potential effects of many PPCPs are unknown.
Microplastics are plastic particles smaller than 5 mm in size. They do not readily degrade and are highly persistent in the marine environment. Effects of microplastics on marine organisms include nutritional stress, digestive system blockage, and entanglement.