Estimation of blood lead levels in the French population using two complementary approaches: Esteban (2014–2016) as part of the human biomonitoring program and the national surveillance system for childhood lead poisoning (2015–2018).

The work carried out by Santé publique France to monitor lead exposure in the French population involves two approaches: biomonitoring studies such as Esteban (health study on environment, biosurveillance, physical activity and nutrition) and the national surveillance system of blood lead levels (SNSPE).  

The Esteban epidemiological study was carried out between 2014 and 2016. It determined lead impregnation levels in the general French population aged 6 to 74 years, analysed determinants related to population exposure to lead, and tracked temporal trends. The previous study to measure blood lead levels in the French population was the National Nutrition and Health Survey (ENNS), which was conducted on adults between 2006 and 2007. In the period between the ENNS and Esteban, the average blood lead level of adults (18-74 years) decreased from 27.5 µg/L to 18.5 µg/L.

The SNSPE, on the other hand, targets children from 0 to 17 years of age at risk of overexposure to lead. These situations of exposure may result from their habitat or living environment (e.g., lead paint), leisure activities (e.g., shooting sports (1)), or lifestyle and cultural practices (e.g., use of traditional remedies containing lead), but also from professional training activities (e.g., apprenticeship in stained glass manufacturing or renovation). This surveillance system includes the mandatory reports of lead poisoning cases and concerns children who have had at least one blood lead test. 

The SNSPE therefore measures the incidence of lead poisoning in children considered at risk of overexposure, which is difficult to capture in biomonitoring studies such as the Esteban study. 

The average blood lead level of children included in the SNSPE between 2015 and 2018 was 18.6 µg/L. This level was 9.9 µg/L for children aged 6 to 17 years, according to the Esteban study. As a point of reference, in its report of 23 May 2014, the High Council for Public Health (HCSP) (2) advocates a policy of reducing exposures to the lowest possible level in view of the non-threshold effects of lead. Its recommendations include a rapid intervention protocol for a blood lead level of 50 μg/L and a vigilance threshold at 25µg/L. However, these levels do not correspond to a lead safety threshold, as this metal is a toxicant considered to have no threshold. Effects on the cognitive abilities of young children have been observed with blood lead levels below the vigilance threshold. It should be noted that these thresholds also concern pregnant women.

The Esteban study showed that, despite a decrease in blood lead levels, the exposition of the population was generalized. Lead was quantified in all analysed blood samples. The search for the determinants of exposure revealed known exposure factors (diet, tap water and alcohol consumption, tobacco consumption (cigarettes), age, sex, housing construction date, parents' professional activity (risk factor for children), etc.). Esteban, for example, showed that children aged 6-10 years were more impregnated than older children (11-17 years), and that girls were less impregnated than boys. The study also showed the persistence of those lead exposure factors already known and described in the scientific literature, and has made it possible to define Reference Exposure Values (REV) (3) for lead. These values serve as a reference for comparing blood lead levels measured in an individual or a subgroup of the French population. It is thus possible to identify individuals who are overexposed compared to the reference population. As an example, in 2019, post-fire monitoring of the Notre-Dame Cathedral in Paris was set up, and the blood lead levels of children screened around Notre-Dame were compared to those of children in the Esteban study (4).

Of the 2,511 incident cases of lead poisoning reported in the SNSPE between 2015 and 2018, one-third resided in French Guiana and nearly one-third resided in Île-de-France. The Provence-Alpes-Côte d'Azur region accounted for nearly 16% of cases. The majority of cases were boys (52% of incident cases) with an average sex ratio (M/F) of 1.11. Children under 3 years of age accounted for 40% of lead poisoning cases, of which 45% were under 1 year of age. 

The main environmental risk factors identified by physicians at the time of prescription were related to old and/or dilapidated housing, the presence of other poisoned children in their environment, and pica behaviour. 

The presence of symptoms was infrequent among incident cases (8%), and mainly consisted of behavioural disorders such as irritability or agitation, sometimes associated with learning difficulties; digestive disorders such as abdominal pain and constipation; neurological signs (headaches, cerebellar ataxia, mental retardation) and autism-spectrum disorders. As clinical signs are not very present and not very specific for lead poisoning, these results show the importance of identifying poisoned children through the search for environmental risk factors.

Lead exposure remains a public health problem in France. Continuing to raise awareness among health professionals about the sources of lead exposure allows better identification of children at risk. The results of Esteban and the SNSPE confirm the need to continue monitoring lead exposure and to continue documenting the associated risk factors. They show that efforts related to public policies (replacement of lead pipes, lead diagnosis in housing, lead-free gasoline, renovation of old housing, etc.) must be continued. Recently, cases of lead poisoning related to metal recovery activities have been identified, requiring the implementation of specific prevention actions (5). 

Given the toxicity of lead and its harmful effects on health, maintaining the lowest possible blood lead levels is a public health issue. The results of the national biomonitoring program are now used to support public decisions to continue efforts to reduce lead exposure (e.g., regulations regarding the presence of lead in housing and drinking water pipes).

The Esteban study showed a generalized exposure to chemical substances in the French population via a substance-by-substance approach, allowing the identification of the determinants of exposure to a chemical product. In the future, it will be important to look at multiple exposures to substances, which will make it possible to assess the reality of exposure to a cocktail of chemicals. In order to verify the continued decline in levels in the general population and evaluate the persistence of risk factors, the next biomonitoring study should include the measurement of blood lead, particularly in young children. It would also be appropriate to obtain, through collaboration with other health agencies, environmental data to couple with biomonitoring data in order to identify emerging sources of exposure.

The most vulnerable populations remain pregnant women and children, including young people in vocational training.