HEALTH AND POLLUTION

Whether it be swimming, drinking water or eating fish, different forms of pollution may affect health.
These pollutions may be varied in nature, with pollutants from several origins: agricultural (pesticide, fungicides, fertilizers, etc.), industrial (sewage sludge, heavy metals, etc.) or other human activities (sunscreen, insecticides, paints, antifouling, motor oils, drugs, etc.).
Here are several phenomena intended to better understand the development and evolution of the pollution in the environment.

Chemical pollution – organic pollution

Chemical pollutions are generally not detectable to the naked eye and it is often difficult to clearly identify their origin. Invisible, we can detect them only by specifically searching through analyses, and their great diversity makes the task difficult. This type of pollution tends to end up in the food chain. Filter-feeding organisms are first affected, then each link of the food chain gets the pollution via direct contact with the skin or by assimilating the pollutants contained in their food. This phenomenon, called biomagnification, leads to a very high concentration of pollutants at the end of the food chain, at predators, including humans. It is particularly the case for mercury pollution.
Unlike other chemical pollution, the effects of organic pollution are often visible to the naked eye. Indeed, these pollutants, frequently assimilated by plants, cause a change in the environment. It may be, for example, a development of algae, causing a less clear water, an accumulation of organic matter on the bottom and a decrease of the amount of available oxygen.

Eutrophication

Eutrophication is the enrichment of water by nutrients, by substances (nitrates and phosphates) promoting the development of plants and, in particular, algae. The decomposition of these plant produces a decrease of dissolved oxygen with, sometimes, stinking gas release. This may result in a reduction of aquatic wildlife, very sensitive to the dissolved oxygen content. Eutrophication is the changeover from a status poor in nutrients (called oligotrophic) to a rich status (eutrophic status). It’s a natural evolution of Lake environments. This aging process is, in general, very slow and occurs at the geological time scale. Human activities can greatly speed it up. It is a dysfunction of the eutrophication process called dystrophisation (or sometimes eutrophication). To get an idea of the amount of algae present, we use a “Secchi disk”, corresponding to a disc painted black and white dove into the water to measure the depth at which it disappears.

Biomagnification

When a toxic product is present, filter-feeding organisms are first affected, then each link retrieves pollution via direct contact with the skin or by assimilating the pollutants contained in their food. This phenomenon, called biomagnification, leads to a very high concentration of pollutants in food chain end, at predators, including humans.