Some of the chemicals below are grouped under the name Persistent Organic Pollutants, or POPs.>

Pesticides are chemicals used to control weeds (herbicides), insects (insecticides), fungi (fungicides) and many other pests. There are several thousand different types used in households, agriculture and industry. They differ in toxic potencies and the way they act and behave in the environment. Some pesticides break down quickly and are less likely to be found in the marine environment. Others can persist over days to years and can accumulate in sediments, water or marine biota.

 

Dioxins are a group of chemicals that are formed unintentionally during many industrial processes. Sources of dioxins include for example waste incineration, pesticide production, burning of plastics or treated wood and vehicle exhausts. There are 210 different dioxins, which differ in toxic potency and potential to accumulate in the marine environment. Most have a very long life time and some readily bioaccuulate in organisms. Therefore, dioxins can often be found at low levels in wildlife, food and humans, as well as in sediments and soil.

PCBs (Polychlorinated biphenyls) are a group of chemicals which are no longer produced but can still be found in the environment. There are 209 different PCBs which have been used in mixtures for many applications such as hydraulic fluids, lubricators and cutting oils, additives in pesticides, paints, plastics and flame retardants and in transformers. Similar to dioxins, PCBs are very stable in the environment and can readily accumulate in sediment, soil and living organisms.

Flame Retardants are chemicals that delay the spread of fires. For this reason, they are incorporated into many materials, such as electrical equipment, furniture, insulation material, plastics and clothes. Today, some of the most common flame retardants used are brominated and include the so-called polybrominated diphenyl ethers. Their toxic effects and potencies are not well understood yet, but some flame retardants can accumulate in living organisms.

 

POPs are among the most hazardous contaminants in the environment. They share many characteristics, the most important ones being the following.

Persistence
POPs can last many years or decades in the environment. This way they can accumulate over time in soil and sediment.

Bioaccumulative
POPs are attracted to organic material, including fats and are not easily metabolised by organisms. Because of this, they can accumulate in tissues of wildlife and humans over time. They can also biomagnify with tropic level, meaning their levels increase through the food chain.

Semi-Volatile
POPs can volatise from soil or water into air. This way, they can be transported over long distances and contaminate ecosystems which are far away from any sources.

Toxic
POPs have been shown to be toxic to fish, birds and mammals, including humans. They can weaken the immune system, cause cancer, disrupt the hormone system and influence reproduction and development of organisms.