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Environmental risks of chemicals

Chemicals are essential to society. Some chemicals, however, are harmful to the environment and to organisms. Although the use of harmful chemicals is restricted, there are still many sources and routes through which they end up in the environment. Different chemicals have different properties. The range of properties is very broad, and some chemicals can cause significant harm to the environment.
Water sample in a plastic bottle.
© Lauri Äystö

PBT substances (Persistent, Bioaccumulative and Toxic) are particularly problematic for the environment. These substances degrade very slowly in nature, and exposure to them may continue for a long time after the emissions have ceased. In addition, many of them can travel long distances from their original emission source.

Some chemicals have adverse effects on organisms even at low concentrations. Others, on the other hand, do not cause significant harm until their concentrations accumulate at the top of food chains. Chemicals can impact the environment and different organisms in very different ways, depending on each chemical’s properties and how it is used.

Many ways to prevent negative environmental impacts

A variety of legislative, economic and voluntary means are used to manage chemical-related risks and harm. In addition to national objectives, legislative measures are also guided by EU legislation and a number of international conventions signed by Finland which aim to reduce chemical-related risks. The environmental administration is responsible for controlling, monitoring and assessing the exposure of the ecosystem to chemicals.

The correct selection of chemicals can also effectively reduce environmental impacts. According to the obligation to choose specified in the Finnish Chemicals Act, the user of a chemical must assess whether it is possible to replace a harmful chemical with another chemical or procedure.

Chemicals end up in the environment via numerous routes

Despite the restrictions imposed, there are still many sources and routes through which harmful chemicals end up in the environment. Emissions may include various point source emissions from industry, wastewater treatment plants or accidents, but also diffuse emissions from households or long-distance airborne transport.

Many large wastewater treatment plants receive not only residential wastewater but also wastewater from industrial plants, hospitals and landfills as well as stormwater from cities. Wastewater treatment plants are primarily designed to remove nutrients and solids from wastewater rather than chemicals. Therefore a considerable proportion of some chemical emissions pass through wastewater treatment plants. For some chemicals and microplastics, a major route into the soil is the utilisation of sludge from wastewater treatment.

Chemicals are also released into the environment from so-called natural or historical sources, which for some substances may be important. These sources include contaminated sediments (organic tin compounds) in the vicinity of ports and shipyards, water areas downstream of former wood processing industries and particularly their sediments (dioxins), land contaminated with fire-fighting foam (e.g. PFAS compounds), or leaching from acid sulphate soils along the west coast (heavy metals). Long-lasting consumer products and construction materials can also form stockpiles from which different chemicals are released despite the limitations or prohibitions currently in place.

Monitoring of harmful substances

The environmental concentrations of persistent and bioaccumulating chemicals are monitored through samples of water and biological specimens. Chemical concentrations are measured in river waters, in bivalve molluscs, in perch (for inland waters and coastal areas) and in Baltic herring (in open sea areas). For rivers, surveys are also taken of various groups of chemicals, including alkylphenols, metals, phthalates, PCBs, PAHs and PFAS. The concentrations of plant protection substances are also monitored regularly in several locations.

Perch in a clear water lake.
Although many substances accumulate in fish, current data indicates that the health benefits of eating fish outweigh the potential harm caused by these substances. © AdobeStock

Combined effects of chemicals

Chemicals can end up in the environment at all stages of their life cycle (manufacturing, use and disposal). It has been estimated that more than 100,000 chemical substances – as well as numerous mixtures of these – are currently in use. Humans can be exposed to chemicals through their skin, through eating, and through breathing. The main route of exposure is through eating. Wild animals are also exposed to chemicals, primarily through eating and drinking.

The risk assessment of chemicals examines the adverse effects of individual substances, but not enough is known about the combined effects of different chemicals. Such combined effects have been thought to be the cause of many environmental and health hazards. Where chemicals cause the same type of adverse effects, they can be mutually reinforcing, which can result in the combined effect being greater than the sum of the chemicals’ individual effects.

The following possibilities have been proposed for the combined effects of chemicals:

  • the combined effect is equal to the sum of the effects of the individual chemicals
  • mutually reinforcing, i.e. the combined effect is greater than the sum of the effects of the individual chemicals
  • mutually weakening, i.e. the combined effect is less than the sum of the effects of the individual chemicals.

The mechanisms through which chemicals impact the body can be complex. Even if the concentrations of individual substances were at levels known to be harmless, the mutually reinforcing effect of different compounds may still lead to adverse effects. In addition, assessing synergies is particularly difficult, as there may be countless combinations of chemicals that cause exposure. 

In risk assessment work, the combined effects of chemicals can be assessed by examining the toxicity of known mixtures or by computationally predicting the possible combined effects. The presence of unknown substances creates uncertainties both in terms of identifying the severity of exposure and the procedures for identification. The procedures suitable for synergy assessment have been published, and it is likely that impact-based bioassays will be part of the environmental risk assessment of chemicals in the future.

Chemical exposure can be measured with biomarkers

Rather than exposure to individual substances, organisms experience within their environment exposure to mixtures of chemicals. Chemical exposure can be measured with different biomarkers that describe changes in organisms at the molecular, cell and tissue levels. This also provides information on the chemical load in the environment.

See also



Finnish Environment Institute (Syke)