Micropollutants: what are these molecules that contaminate our water?
Today, our aquatic environments are polluted by numerous types of waste and chemical molecules. Some of this pollution is invisible to the naked eye. These are known as micropollutants. They are chemical molecules found in aquatic environments in very low concentrations.
Geoffroy Duporté, University of Montpellier
By way of comparison, the mineral salts contained in drinking water, such as calcium, potassium, and magnesium, are present in concentrations that are one thousand to one million times higher than those of a micropollutant.
The concentrations of these micropollutants are equivalent to a sugar cube in an Olympic-size swimming pool. Obviously, if you drink the water, you won't taste the sweetness, but unfortunately, even at these tiny concentrations, some of these molecules can have negative effects on the environment, living organisms, and biodiversity due to their toxicity, persistence, and accumulation.
Where do micropollutants come from?
There are many sources of micropollutants in the environment. Although there are natural sources (such as volcanoes, which emit large amounts of hydrocarbons), micropollutants are generally man-made (from industry, transportation, agriculture, and domestic use).
Currently, more than 100,000 molecules are identified as micropollutants by the European Union. Many products we use on a daily basis contain them: cosmetics, medicines, cleaning products, paints, etc.
The origins of water contamination by micropollutants are therefore very diverse:
- Domestic wastewater plays an important role in transferring these contaminants to aquatic environments. Although wastewater treatment plants are capable of removing some micropollutants, certain molecules reach aquatic environments without being eliminated. These include drug residues (paracetamol, antidepressants, etc.), phthalates (molecules derived from the use of plastics), parabens (derived from cosmetics), UV filters present in sunscreens, and pesticides such as antiparasitic products used for domestic animals are examples of micropollutants commonly found in domestic wastewater.
- Industrial wastewater also discharges numerous pollutants related to the activities concerned (plastics, detergents, solvents, petroleum products, metals, etc.).
- Hospital wastewater also contributes to the contamination of wastewater with pharmaceutical residues. These include numerous antibiotics, anticancer drugs, and contrast agents.
- Contaminants can also originate from agriculture, with soil pollution from pesticides or antibiotics given to farm animals. These micropollutants contribute to the contamination of aquatic environments through runoff or infiltration.
This pollution converges in groundwater, rivers, seas, and oceans. This invisible pollution is thus also found in our drinking water resources.
The fight against micropollutants is now an environmental and health issue. To illustrate this problem, a scientific study shows the ubiquity of pharmaceutical residues in 258 rivers around the world. The most commonly found molecules are carbamazepine (anti-epileptic), metformin (anti-diabetic), and caffeine. This study shows that in 25% of the sites studied, the concentrations of at least one pharmaceutical residue were higher than the concentrations that cause impacts on aquatic organisms.
For example, another scientific study assessed caffeine residues in aquatic environments as a contaminant of concern. This compound has been found in the tissues of coastal and marine organisms (microalgae, coral reefs, mollusks, and fish). Furthermore, it has been shown that these caffeine residues can, for example, affect the reproduction and development of aquatic organisms.
This article is published as part of the "Questions from Young People in Research initiative led by Agropolis International in partnership with the Montpellier Academy Rectorate.
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Geoffroy Duporté, Senior Lecturer in Environmental Chemistry, University of Montpellier
This article is republished from The Conversation under a Creative Commons license. Readthe original article.