Contamination is “the presence of elevated concentrations of substances in the environment above the natural background level for the area and for the organism” (Sciortino and Ravikumar 1999). Contaminants (or chemical pollutants) represent a significant threat to the environment and marine mammal populations. In addition to their direct toxicity, environmental contaminants such as POPs and mercury may affect the reproductive, immune and nervous systems of organisms and some can cause cancer. The huge number of synthetic chemicals introduced into the environment and the ways they may interact with each other (cumulative effects) make it difficult to establish whether and when they cause adverse health effects and their potential impacts on marine mammal populations.
POPs include PCBs, pesticides (like DDT), insecticides, polycyclic aromatic hydrocarbons (PAHs) which are by-product of incomplete combustion of organic matter like oil and coal, as well as emerging pollutants like brominated flame retardants. They have dioxin effect and are extremely toxic substances for human and environment health. They are highly soluble in lipid (fat) and accumulate in fatty tissues. POPs and heavy metals (such as arsenic, cadmium, lead and mercury) are very little metabolised and thus only slowly eliminated. They are resistant to environmental degradation and remain in the environment years after their release. They travel long distance from their sources and their stability give them ubiquity and capacity of bio-accumulating up the food chain – their concentration and thus toxicity increase from one predator level to a higher one.
POPs and heavy metals interfere with and disrupt the endocrine (hormone) system, they are called ‘endocrine disruptors’. They can disturb the immune system – decreasing resilience and increasing susceptibility to disease, the reproductive system – decreasing reproductive success, and the central nervous systems – affecting development and orientation for example.
Despite regulations and mitigation measures to reduce PCB pollution, PCBs continues to cause severe impacts among cetacean top predators in European and other seas (e.g., Murphy et al 2015, Jepson and Law 2016, Jepson et al 2016). New data show a correlation between present reproductive failure in European harbour porpoise, killer whale and bottlenose dolphin populations and (PCBs) burdens.
This is European waters, but the problem is that POPs including PCBs are not static, they do not remain close to their sources. They transfer over long distances from industrialised to non-industrialised regions. They travel to the Arctic and Antarctic, which are the recipient of contaminants whose sources are thousands of miles away. There, the highly fat-soluble contaminants concentrate as they make their way up the high-fat food Arctic and Antarctic food chains. Remoteness and the absence of indigenous pollution sources do not guarantee the viability of wildlife populations and the well-being of northern communities.
In Svalbard in recent years, polar bears show decreased levels in vitamin A and some antibodies, and 1.5% of sampled females have partially-developed male sexual organs – pseudohermaphrodites (e.g., Wiig et al 1998). East Greenland polar bears exhibit reduced bone density (osteoporosis) and size reduction in sexual and reproductive organs (Sonne et al 2012). Both believed to be the result of high concentrations of long-range environmental contaminants.
Chemicals are an integral part of everyday life with over 100,000 different substances in use, and new ones constantly emerging. There is hardly any industry where chemical substances are not implicated and there is no single economic sector where chemicals do not play an important role. Therefore, their sound management is essential.