Abstract

Via the air, water, food and skin, people and the environment come into contact with different chemical substances at the same time. This can be harmful. For many substances, we know whether they are harmful and at what level of exposure. Less is known, however, about the consequences for people and the environment of simultaneous exposure to multiple different substances.

RIVM has therefore conducted a study to identify which methods are able to take account of the potentially harmful effects of added exposure to substances via water or the air. The emphasis of the study was on the emission of chemical substances by industry. At present, these substances are only tested individually to assess whether the concentration remains below the maximum permitted level.

RIVM identified two types of methods which could be used for policymaking. There are methods that calculate the likelihood of harmful effects following exposure to a mixture of substances in water or the air. And there are methods that more strictly assess the effects of the emission of a single substance. This is achieved by preventively taking into account of the harmful effects of different substances or exposure to a single substance via different sources or exposure routes, such as traffic, food intake and drinking water.

The calculation methods offer a first impression of the likelihood of effects of mixtures in air or water. They also identify which substance in the mixture makes the greatest contribution. Using this information, policymakers and businesses can take more targeted measures to reduce the emission of substances and consequently to mitigate the risk of adverse effects. The calculation methods are technical tools that can be used in the licensing process. An essential precondition is that the relevant authorities have sufficient data and knowledge to be able to calculate the impact of a mixture.

RIVM recommends the further practical elaboration of the calculation methods and to also include the potential effects of non-chemical factors such as noise, odour and particulate matter. The preventive methods are easy to use, but there is still uncertainty about whether they make the assessment too flexible or too strict.

It is also possible to combine the two types of methods. This approach allows taking account of both the harmfulness of the mixtures and the contribution made via different sources and routes. More work is needed to investigate precisely how this can be done.