A new study of pollutants in Mediterranean coastal waters assesses the risks posed by difficult-to-detect chemicals present at low concentrations. Coastal monitoring programmes may be required to control discharges of some of these pollutants, which, at current levels, could be harmful to sensitive marine creatures.
Organic micropollutants encompass a wide range of carbon-containing chemicals, which, until recently, were hard to detect in the environment. Powerful new methods have now made it possible to detect several different micropollutants at very low concentrations, down to nanograms per litre of water.
According to the researchers, their study suggests that the area of the Catalan coast between Roses and Valencia in north-eastern Spain is a ‘hotspot’ for organic micropollutants. They measured concentrations of 51 different compounds in rivers, wastewater and seawater in the region. In seawater, alkylphenols, bisphenol A (BPA) and phthalate compounds were at levels high enough to pose a significant risk to some marine species.
Alkylphenols have a broad range of industrial, domestic and agricultural applications, including in plastics and detergents, although EU Directive 2003/53/EC restricts their use to concentrations lower than 0.1%. Treatment plants are usually more than 95% efficient at eliminating alkylphenols from wastewater. However, untreated water from urban and industrial sources may increase concentrations entering the coastal environment. Phthalate esters and BPA are used to make plastics, paints, glues and inks. BPA is an endocrine-disruptor, which means that it can interfere with the hormonal system in animals.
Significant levels of organic micropollutants entered the marine environment via wastewater treatment plants and pollutants were usually carried to the sea by rivers. Two of the eight wastewater treatment plants, from which samples were taken, treated water from the largest cities in Catalonia and were major contributors of micropollutants.
Algae, fish and mysid shrimps, were chosen as representative organisms for assessing potential risks of organic micropollutants to marine life. The researchers compared the actual concentrations of chemicals measured in Catalan coastal waters to those known to be toxic to these organisms, in order to produce an estimate of the risks they were exposed to at each site.
At one particular sampling site in Barcelona Port, mysid shrimp appeared to be exposed to clear adverse effects, and at a third of the sites overall, they faced significant potential for adverse effects. By contrast, algae and fish were only potentially at risk in a few sites. At the Barcelona Port site, the potential risk to fish was more significant.
The researchers say their study underlines the need for better monitoring and management of micropollutant concentrations in the region, which receives water from urban and industrial sources in 22 different countries. The enclosed nature of the Mediterranean Sea makes it particularly susceptible to problems caused by uncontrolled discharges.
Source: Sánchez-Avila, J., Tauler, R. & Lacorte, S. (2012). Organic micropollutants in coastal waters from NW Mediterranean Sea: Sources distribution and potential risk. Environment International. 46: 50-62. Doi: 10.1016/j.envint.2012.04.013.