Blood, nails and urine show which toxins people ingest

Blood, nails and urine show which toxins people ingest

Changing groups of Flemish people have structurally donated blood, urine, hair or nails since 2002. Scientists determine the presence of more than 200 potentially harmful chemicals. It gives an idea of ​​what substances the general population ingests and what accumulates in their bodies. Targeted policy can be made for this. The aim is to reduce exposure to harmful substances.

The Netherlands does not have such a structural measurement program. Or, not anymore. It was abolished in 1997. While the government has a legal obligation to protect and promote the health of people, animals and the environment, the Health Council recently wrote in a report. She recommends the design of a program that will structurally monitor the presence and concentration of chemical substances in the Dutch population.

Measuring chemicals in the human body is called human biomonitoring. It can happen incidentally or structurally. The Netherlands now only monitors in response to incidents, say biostatistician Eva Govarts and biomedical scientist Liese Gilles of the Flemish Institute for Technological Research (VITO), which plays an important role in the Flemish structural measurement program. Such as in 2017, when the substance fipronil, banned in the food sector, suddenly appeared in eggs. “You then measure only one or a few substances, in a specific group of people. You cannot draw any conclusions from this for the general population.” Such an approach focused on incidents can be harmful to citizens’ confidence in the government, the Health Council writes.


Govarts and Gilles coordinated a study between 2016 and 2022 to coordinate human biomonitoring in 23 EU member states. “So that measurements in those countries can be compared with each other,” says Gilles. It came to light that the concentration of arsenic in 40 percent of teenagers exceeds guidance value (below that value, according to current insights, no health risk is expected). In one-tenth of all individuals examined, PFAS and cadmium, among other things, exceeded that value. The results were published in the trade journal last year International Journal of Hygiene and Environmental Health.

The Flemish program has successive campaigns. The fifth is now running until 2027. Each time it is determined which groups are investigated. There are a maximum of three: newborns and their mothers, adolescents (14-15 years) and adults. The group of participants is new every time. Gilles: “Because after 4 or 5 years, an adolescent is no longer an adolescent.” And the research wants to investigate the presence of chemicals in certain age groups, given the sensitivity to certain substances in different stages of life. “You can also continue to follow the same group of people over time,” says Gilles. But that is a different type of research. “For example, if you want to investigate whether exposure to a certain substance during pregnancy has an effect on the development of asthma or allergies ten years later.”

Plasticizers and flame retardants

During monitoring, (umbilical cord) blood, urine, hair or nails are taken from the participants. So-called biomarkers are then determined. These may be the original chemical substances, as is the case with bisphenol A. But more often they are metabolites, compounds that are formed after conversion in the human body. For example, 3-PBA is a known metabolite of pyrethroids.

Each campaign has new accents. The first examined traditional pollutants such as dioxins, PCBs and PAHs. This happened in eight types of areas, including the agglomerations of Antwerp and Ghent, a fruit region, a region with many incinerators, and the Albert Canal zone where there are many chemical companies. In the second campaign, the number of biomarkers increased to more than fifty. More recent contaminants were also included, such as plasticizers, fire retardants and newer pesticides. The areas studied included three hot spots, Genk-Zuid, the Menen region and the Ghent canal zone, with a large metal industry, scrap processing and particulate matter-producing industries respectively.

The researchers were already able to draw all kinds of conclusions from these first two campaigns. Participants from urban areas had higher concentrations of cadmium, lead, manganese and mercury in their bodies. Burning open fires could be associated with higher values ​​for dioxins. “Fish consumption leads to higher levels of toxic relevant arsenic and mercury in the body,” states a brochure produced after the second campaign (2007-2011).

Annoying trends

This brings Govarts and Gilles to a crucial aspect: the results provide the Flemish government with tools to intervene in a targeted manner. As happened with persistent organic contaminants (POPs), a broad group of chemical compounds including DDT, PCBs, and dioxin-like substances. After the first campaign, the concentration of these substances turned out to be significantly higher in rural areas, in all age groups. And despite declining concentrations of these compounds in the broader population, their health effects (disruption of the endocrine system and fetal growth, and increased risk of asthma) were still seen during the first and second campaigns. Existing policy was then tightened and new policy was introduced, describes a 2017 publication. For example, additional inspections were carried out at farms for banned pesticides. In some rural areas, breast milk was screened for the presence of chlorinated compounds. The regulations for burning open fires were tightened. And there were information campaigns about the use of (banned) pesticides, about the responsible production of crops and eggs in your own garden, and about the consequences of wood burning.

“After the introduction of policy, you see some connections decrease nicely over time,” says Gilles. But the measurement program also reveals another trend, say Gilles and Govarts. As they have seen with bisphenol A, a substance used in the production of flame retardants, printing inks, plastics such as baby bottles, and coatings for the inside of food packaging, among other things. Even at low exposure, bisphenol A appeared to have a possible harmful effect on the immune system of unborn and young children. In Europe, the use of the substance has been banned in a growing number of products – such as baby bottles, cosmetics, thermal paper – since 2011. Last year, the European Food Safety Authority (EFSA) concluded that bisphenol A in food poses a health risk to all age groups. “In response, we see alternatives to bisphenol A emerging and increasing in the population,” says Govarts. The question then is whether they are not equally harmful. “New research is needed,” says Govarts. “Toxicological studies, epidemiological studies. That takes years.” They have seen the same with some phthalates (plasticizers) and PFAS. “We are lagging behind the facts,” says Gilles. The chemical industry can draw on 350,000 different substances. “We have a good knowledge base about toxicology from just a fraction.”

Cheap plastic products from China can be a risk

Another important part of the Flemish measurement program is communication. Before the findings of a study are shared with the press, the government and the Flemish population, the participants are told the results. “These could be the individual results,” says Govarts, “but also the information for their region or their age group.” Information evenings are organized where they can ask questions. That includes doctors. On such an evening, participants also receive tips to limit their exposure. “It is tempting to buy products via sites like AliExpress,” says Gilles. But in China, for example, the rules for chemicals are less strict. “During those evenings we draw people’s attention to this. It is up to them whether or not to do something with it. But we notice that people often take such advice to heart.”

Govarts and Gilles think that this communication is good for confidence in the government. But more research is needed. The current European project for human biomonitoring, which runs from 2022 to 2029, therefore focuses not only on improving measurement methods and new ways to calculate the risk of substances. It also tests different ways of communication.