Sources of micropollutants
Micropollutants refer to residue from substances, use everyday in modern society, including for example pharmaceuticals and personal care products (PPCPs), hormones, pesticides and industrial chemicals. Residue from these can be found in water bodies everywhere.
Hazardous micropollutants usually end up in wastewater treatment plants (WWTPs) as a result of domestic uses of textiles, electronics, pharmaceuticals, and cosmetic and hygiene products. Other sources are industrial discharge, stormwater runoff from cities, and surface run-off from agricultural areas. Studies show that 70 percent of the pharmaceutical residue in the wastewater comes from household use, while 20 percent comes from livestock farming, and only 5 percent from hospital effluent, the remaining 5 percent is runoff from non-specific sources. This said, variations might be large in different regions and countries.
Independent of source a large degree of the micropolloutants end up in our waters because they are persistent and not bio-degradable. The persistence and non-biodegradable nature of these contaminants means that if release into the nature the substances will pass through the soil and end up in the groundwater. Even if released to the wastewater treatment plant the the main part of the pollutants its release with wastewater effluent and end up in the surface water.
Impacts of micropollutants on the environment
Existing biological wastewater treatment plants are not specifically designed to remove micropollutants therefore discharges from WWTPs is considered as major point source of these chemicals in our environment. The occurrence and continuous input of organic micropollutants in receiving waters including groundwater is a growing environmental issue. As they are known to be non-biodegradable, persistent and bioaccumulative, many of them have been identified as potential threats to aquatic species and animals and probably to human health.
The presence of micropollutants in the environment has been linked to toxic biological effects including estrogenicity, mutagenicity and genotoxicity.
Studies have shown that feminization of male fish is an obvious example relating the impact on fish population exposed to endocrine disrupting compounds (EDCs). The continuous release of EDCs into the environment, even at very low levels, may give rise to reproductive and developmental abnormalities on sensitive species.
Another serious concern nowadays is the rise of antibiotic-resistant organisms in the environment, posing additional hazard to the microbial ecosystems. There has been increasing evidence on the occurrence of antibiotic resistant genes in different environmental matrices due to intensive use of antibiotics for human and animal health.
As a consequence to the growing population and high dependence of modern societies on chemicals especially pharmaceuticals, the amount of micropollutants in the environment is still expected to increase in the coming years. The risk of exposure to complex mixtures is more alarming than single compound due to probable synergistic effects.
Reducing micropollutant concentrations requires a long-term strategy
There are currently 100 000 commercially registered compounds in Europe and residue from the majority of these will eventually end up in the water cycle. Furthermore the production of chemicals is predicted to increase.
There are at least two different approaches that need to be adopted to reduce concentrations of micropollutants in the long run – source control and end of pipe removal. Source control is a long-term measurement that include prohibiting toxic contaminants and promoting green chemistry. When it comes to pharmaceuticals, prohibition of effective drugs is an ethical dilemma as both humans and animals may rely on these for their survival. End of pipe solutions, i.e. wastewater treatment, will thus also in the long run be of high importance.
The European Union is taking action
Within the European Union legislative action is taken and a list of prioritized substances that are seen as a threat to surface and ground water has been published. To live up to the environmental standards laid out by EU, member countries needs to monitor the prevalence of the substances on this list, starting in September 2015. (Directive 2013/39/EU (priority substances in the field of water policy) and Directives 2000/60/EC (Water Framework Directive))
Switzerland is one step ahead and has already decided to reduce micropollutants and toxicity in their wastewater. They have decided to upgrade 100 WWTPs (which represents about 50% of the municipal wastewater in Switzerland) during the next 20 years.