Identifying sources of lead exposure for children, with lead concentrations and isotope ratios.

Despite a dramatic decrease in children's blood lead levels (BLL), lead exposure remains a public health concern because increasing evidence shows effects at very low doses. Lowering BLL still further requires the identification of lead sources and, therefore, new tools to investigate and thus prevent exposure. We describe a procedure that uses both lead concentrations and isotope ratios (IRs) to identify sources of overexposure in homes. Water, dust, and paint chips were sampled from the homes of 21 children with elevated BLL from Aubervilliers (Paris metropolitan area). Lead concentrations of concern were calculated from reverse physiologically based pharmacokinetic modeling for water and dust. Isotope ratio matching of blood and environmental samples (with a lead content above the concentration of concern) was performed by computation of the distance between their IRs. When the IR of the source did not match that of the blood, the source was eliminated as a source of lead intoxication. The number of sources eliminated (per child) due to lead concentration ranged from 14% to 86% (mean 66%) for dust, and 100% for water samples. The number of remaining potential sources eliminated by IR interpretation varied from 0% to 100% for both dust and paint chips (mean 63% and 58%, respectively). IRs made it possible to eliminate at least one source in 20 of 21 cases and identified a single source in 11 of 21. The number of dust and paint sources not eliminated by concentration or IR varied from 8% to 45% (median 18%). The pilot study supports the usefulness of these procedures and the added value of IRs for identifying sources of lead poisoning. However, systematic use should be supported by cost-effectiveness analysis on a larger and more representative population of elevated BLL.

[Evaluating the effectiveness of child lead poisoning prevention programs]. / Evaluation des résultats d'actions de prévention du saturnisme infantile.

PROBLEM: A multi annual screening and prevention program against lead poisoning was implemented in a suburb of the Paris area. We attempted to assess the effectiveness of this program based on data available from children screening and follow-up. METHODS: Indicators of effectiveness included the evolution of blood lead levels at screening and the frequency of secondary increases in blood lead levels. Buildings inclusion dates were used to control for the increasing selection of less exposed children. RESULTS: A total of 3,660 children were screened between 1992 and 2000. We observed a regular decrease in blood lead levels at screening, in the highest blood lead levels obtained for each child and in the proportion of children whose blood lead levels increased after screening: the proportion of children with initial blood lead levels >=15 micro g/dl fell from 17.4% in the 1992-1996 period to 4.1% in the 1997-2000 period. A multivariate analysis taking into account the first year that children were screened in a given building showed that less exposed children were included over time, but found also an additional independent decrease in blood lead levels that can be related to the effectiveness of prevention efforts. A "building by building" analysis of 30 buildings where more than 20 children were located over the whole study period confirmed that the incidence of lead poisoning decreased within most of these buildings. CONCLUSIONS: Taking into account buildings'inclusion dates makes it possible to distinguish program effectiveness from the consequences of including less exposed children The effectiveness of preventive actions is associated with several interacting factors, including the participation of families and the active involvement of local technical staff and policy makers. The finding that the decrease in blood lead levels leveled off after 1997 calls for further actions.

[Screening for lead poisoning in children by measuring lead levels in housing: a study of the Paris region]. / Dépistage du saturnisme infantile à partir de la recherche de plomb dans l'habitat: une étude en région parisienne.

Screening programs for lead poisoning in France rely usually on the preliminary identification of risk factors among children seen in Maternal and Child Health (MCH) clinics. To assess the potential relevance of screening strategies based on the quantification of exposure to lead in housing, we estimated first the prevalence of exposure to lead in a representative sample of older buildings, then the prevalence of lead poisoning among children living in those buildings where high levels of lead had been found. Exposure to lead was measured in dust and paint samples collected in hallways and other collective areas of the buildings. Venous blood samples were collected from the children aged 10 months to 6 years residing in buildings where lead exceeded 1.5 g/kg in paint samples or 1000 micrograms/m2 in dust samples. Paint and dust samples were collected in 137 buildings: 74% presented high dust and/or paint lead contents. Blood samples were collected from 145 out of a total of 189 children residing in these buildings: blood lead levels (PbB) were higher than or equal to 10 micrograms/dl for 65% of these children; 29% were higher than or equal to 15 micrograms/dl, 16% higher than or equal to 20 micrograms/dl. Out of 42 children with PbB > or = 15 micrograms/dl, 21 had not been previously identified through the screening program conducted in local MCH clinics. Clinic-based and environment-based screening appeared to be complementary. It seems thus justified to develop screening strategies based on the assessment of exposure to lead in the environment.