You cannot see it, but the soil contains a wide range of chemical substances. Although some of those substances are natural, a large number have been added to the soil by people. Many of those chemical substances have been deliberately added to the soil, for example due to fertiliser usage, and are important for the proper development of agricultural crops. However, some other chemical substances are unnecessarily in the soil and have ended up there due, for example, to industrial activities. Higher concentrations of these substances can be dangerous. If humans ingest those substances, they may cause diseases. What is more, organisms in the soil, which perform all kinds of important tasks, may be hindered and even die due to the presence of these chemical substances.
The soil may also have been fertilised by manure and excrement from infected farm and wild animals. Unpurified or insufficiently purified waste water may also have a detrimental influence on the microbiological quality of the soil and this may lead to risks for humans. The excrement may contain eggs of the Toxocara canis roundworm (dog parasite) which can cause diseases among children. People may also become ill due to a toxoplasmosis infection via cat excrement.
If chemical substances in the soil or the groundwater represent major risks to people's health or soil life or are likely to be distributed via the groundwater, this may be a reason to tackle a contaminated location in an operation referred to as remediation. At its peak, in 2004, there were 650 thousand seriously contaminated locations. Since then most of these locations have been investigated. Often there was no evidence of serious soil contamination. Remediation was performed in a total of thirty thousand cases at locations with so-called urgent soil contamination. This involved the contamination being removed or isolated. In the Soil and Substrate covenant government bodies agreed that the remaining 1,400 locations with urgent soil contamination will be remediated and/or controlled by 2020.
Bodemloket provides a map of the Netherlands showing where historical activities may have resulted in contamination of the soil and groundwater. It also shows where research and remediation have taken place.
Soil contamination and health
Damage to health in the event of exposure
Living, working or recreation at a location with soil contamination almost never results in serious health problems. That is because insufficient quantities of these chemical substances from the soil actually enter people's bodies ('exposure'). However, contaminated ground can make illnesses more likely if we come into direct or indirect contact with contaminated soil or products which come from the soil. This could happen during gardening or digging work.
Direct and indirect exposure
People can come into contact with contamination in the soil or groundwater via various exposure routes. This not only involves direct contact with the soil, but also indirect contact such as inhaling contaminated articles, drinking contaminated groundwater or eating contaminated vegetables from the garden.
How contaminated soil is used determines the degree of exposure. For example, the consumption of cultivated vegetables grown on contaminated soil in a contaminated vegetable garden can cause health issues. Similarly, health issues can occur after breathing in volatile contaminants which move from the ground water to the surface of the soil or accumulates in people's homes. Another example of risks of health damage occurs if contaminated drinking water is consumed, for example from a private drinking water well. Lastly, chemical substances attached to soil particles can enter children's bodies through hand to mouth contact, for example while they are playing on contaminated soil.
The parties involved
The state, provincial governments and municipalities, including the Municipal Health Service, are working together to assess chemical soil quality and cooperate if the risks are excessive and action has to be taken (in the form of a soil remediation operation). The research institutes play a role in the development of the required instruments. The consultancies generally carry out the soil investigation which involves, for example, taking and assessing soil and groundwater samples.
In the first instance the party that has caused the soil contamination is held responsible. This means that it has to pay for the investigation and any remediation work. Often, several parties are responsible for an incidence of contamination and in many cases no one will know who actually caused it. The government only pays for the soil to be made suitable for use if no party can be held accountable.
Assessment of soil contamination
Chemical substances that have been detected are not always a problem and therefore do not, by definition, have to be removed. A risk assessment can be carried out to check whether, at a contaminated location, and excessive risk actually exists in terms of damage to people's health, effects on the soil ecosystem and the spread of substances via the groundwater. A standard instrument is available to do this, namely the decision support model called Sanscrit. Certainly if there is less intensive contact with ground and with products from the ground, for example, as on an industrial estate, the presence of chemical substances can often do little harm.
For people who want, or are going, to communicate about soil, both with regard to the possibilities which the soil offers and with regard to the threats facing the soil, there is a brochure entitled Communicate about soil: possibilities and threats. Clarification of the concepts of soil contamination risks and standardisation.
- Your provincial government or the municipal authorities can tell you which nearby locations are, or are suspected of being, contaminated. Sometimes the municipal authorities will have commissioned an operations unit or environmental authority to carry out this task.
- Are you buying a house or a piece of land? If so, you should check whether a declaration of suitability or a 'clean soil declaration' is available. If this is not the case, an assessment will have to be made to determine whether the site is contaminated.
- You yourself should also look out for indications that the soil is contaminated. For example, have any oil barrels leaked onto the site, or has a path been laid using rubble which may include broken pieces of asbestos?
- Make sure the soil is clean before you start a vegetable garden.
- If you are going to build or extend, a soil survey will often be necessary in order to obtain a building permit.
- Do you live on contaminated soil which is being cleaned up? If so, you can set up a residents group to represent your interests.
- You can also take steps yourself to prevent any new soil contamination. Be careful with substances which can cause contamination such as oil and petrol.
- If you suspect soil contamination, you should report this immediately to the municipal authorities.