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This image shows hazardous chemicals being emitted into the ocean.

Types of chemical pollutants

In the previous step we have discussed how chemicals that we use may find their way into the ocean. Here we will examine a couple of the many types of chemical pollutants that we find in our oceans and the properties that that help us determine which are of the most concern.

Persistent organic pollutants (POPs)

As the name implies, POPs is the name given to chemicals that have been identified to persist for very long periods of time in the environment. In the 2001 Stockholm Convention, an agreement was reached to outlaw or limit the use of 12 POPs known as the dirty dozen. The rational for banning was based upon PBT criteria.

P stands for persistent, the ability to last in the environment for longer periods of time. B stands for bioaccumulative, or the ability to partition into fatty tissues in organisms where they pass up the foodchain in increasing exposures. Finally, the ‘T’ stands for toxic, which relies on evidence that shows these compounds have the ability to harm both ecosystem and human health. Although these compounds are banned, illicit use combined with their long lifetimes in the environment contribute to these compounds continuing to be a concern today.

Heavy metals

Heavy metals are naturally occurring and many have high value to industry when extracted from the earth. However, similar to POPs, these compounds are a concern due based on the same PBT criteria. Often released from mining operations and oil spills, natural and unintended which we will learn about later. Heavy metal contamination can move up the food chain where their exposure can result in a major human health concern.

Emerging contaminants

The rapidly increasing use of chemicals in our every day lives is evident by our increasing use of pharmaceuticals and personal care products. Many of these chemicals are designed to be bioactive, having the ability to impact biological systems, in humans. However, many of the same receptors that these chemicals target in humans also occur in aquatic organisms.

When we consume pharmaceutical chemicals, only a small portion are used by the human body. The rest are excreted in our waste which is transported to wastewater treatment facilities through the sewage network. Wastewater treatment facilities, developed many decades ago, have not been designed to remove these types of waste products and therefore, they may pass through the treatment facility where they are released either in rivers or streams or directly into the ocean.

Scientists are only beginning to understand the impact these contaminants have on aquatic systems like the marine environments.

Nutrients

Other types of chemical pollutants come in forms that we may not consider pollution at all. Excess nutrients that we use in agriculture to increase yields, or in our own gardens to ensure lush green grass, can be washed away and end up in rivers. When erosion occurs, the process where soil is washed away in runoff into rivers or directly into the ocean, even nutrients bound to the soil can enter marine environments.

In the next step we will investigate how excess nutrients can have disastrous impacts on marine environments.

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This article is from the free online course:

Tackling Environmental Challenges for a Sustainable Future

University of York