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Marine pollution: what impact on the environment and human health?

In addition to ocean acidification, wildlife and marine flora are seriously threatened by the increasing spill and release of toxic pollutants in the marine environment. What are these pollutants and how do they act on the seas? How the IAEA does it contribute to the monitoring of these pollutants?

It is easier to characterize pollutants sailors by their impact:

” any substance introduced in the oceans and having unwanted effects. “

IMO, 2019

What pollutants act on the seas?

Defining what a pollutant can be difficult because the term applies to many substances besides toxic industrial by-products. It is easier to characterize marine pollutants by their impact: any substance introduced into the oceans and having effects not desired.

This broad definition includes metals heavy, such as lead and mercury, and compounds
synthetic organic like chlorinated pesticides, flame retardants and polychlorinated biphenyls (PCB), but also certain elements essential to life, like nitrogen and phosphorus compounds.

These pollutants may have been discharged directly and illegally in the oceans as waste or have been transported there by processes more difficult to control like winds,
runoff and river water. Thanks to a careful monitoring and strict regulations, governments hope to control harmful pollutants entering the seas.

How do heavy metals act on organisms?

If heavy metals like lead and mercury can be fatal when ingested in large quantity over a short period, most heavy metals harm marine life by reducing generally the longevity of organizations, as well as their “recruitment”, or their ability to have a descendants who survive them.

Reducing the duration and recruitment of key organizations eakens
considerably the ecosystem, making it more vulnerable to other threats like verfishing, changes or ocean acidification. Degradation of the marine environment is often attributed to the combination of these disruptive factors rather than a single cause.

How do nitrogen and phosphorus compounds work on organisms?

Nitrogen and phosphorus, natural elements essential for life and plant growth are components fertilizer keys. When you use too much fertilizer in fields, rainwater can wash away the surplus nitrogen and phosphorus in river water then to the sea. These nutrients can then make explode populations of phytoplankton, phenomenon which we call “proliferation” of populations.

The toxic algae can then transmit toxins to fish, which can then be eaten by the man. In some cases, this overeating, or “eutrophication”, may increase the population of some species at the expense of others. The proliferation of toxic algae can cause a oxygen deficit in some areas due to the decompose planktonic biomass and thus create “dead zones”, anaerobic zones where fauna and normal marine flora cannot survive.

Where do the pollutants go?

When organisms ingest and retain more pollutants and toxins that they cannot remove, “Bioaccumulation” occurs. In the food chain, pollutant concentrations tend to increase in the organism of large predators (biomagnification).

The human being, at the top of the food chain, runs a great risk of accumulation of high concentrations pollutants in his body tissue. Works research carried out on large predators of the marine environment (large fish, seals and birds) help us understand the process of biomagnification and to assess the health security of sea products.

How can nuclear techniques mitigate pollution?

Domestic sewage and solid waste which result from their treatment can be dangerous for human health and the environment if they are not managed properly. At the same time, the waste solids from wastewater contain valuable organic matter and nutrients, which could enrich the soil and turn out to be a resource important as long as they can be treated in a way adequate to avoid risks and to be used in all safety, in accordance with good practice.

Sewage sludge can now be treated using gamma rays produced by a source at cobalt 60 or an electron accelerator, to remove pathogens (causing disease) present in this sludge such as bacteria, fungi or virus. This nuclear application allows to reject sludge into the environment safely. A pilot gamma sludge irradiation facility is in service in India.

This process makes it possible to obtain sludge dry, pathogen-free, suitable for use
advantageously as a fertilizer in agriculture. The Field tests at Baroda have confirmed that this fertilizer increases agricultural yields and improve soil conditions.

How does the IAEA help?

The IAEA helps its Member States use nuclear technologies to monitor soil and sea pollution. The IAEA Environmental Laboratories use radioisotopes to find and track sources of pollutants and thus help countries control their impact on the environment. For example, the IAEA supported a study effects of traces of cadmium (toxic metal) on fish and shellfish in Chile1 .

Experiments have been designed to use cadmium 109 as a radiotracer to measure the speed with which the cadmium present in the molds is rejected in order to understand the bioaccumulation of this dangerous metal.