The aim of this paper was to provide an economic evaluation of the health impacts of children with lead exposure in France. Based on the assumption of the EFSA report , that there is no threshold of lead exposure, our study provides a range of annual benefits and partial costs estimated in order to highlight the economic impact for society of lead exposure reduction policies below the conventional B-Pb screening value of 100 μg/L. Several hypothetical threshold values for intoxication (15, 24, 100 μg/L, respectively) were chosen following a "what if" approach. We have no strong data to choose levels lower than 15 μg/L but also do not assume it to be a safe exposure level. The partial cost benefit analysis documents a clear cost effectiveness of lead hazard control, which should result in benefits greatly superior to the costs, as suggested by the comparison of the sum of benefits to that of congruent costs for one year. This study showed that by reducing childhood lead exposure, large social benefits might be produced for the birth cohort of 2008 (and subsequent years): € 22.72 billion, € 10.72 billion and € 0.44 billion, respectively. The benefits were mainly due to the social avoided costs, specifically the lost life time earnings, at exposures corresponding to B-Pb <100 μg/L. There are some limitations to our analysis, due in particular to access to figures related to avoided costs and to costs of exposure reduction as we will see below. This is the reason why we could not perform a complete CBA. Direct health costs were also estimated but they were probably underestimated. Lead exposure provokes other health impacts besides cognitive disorders which were not assessed in this paper, such as cardiovascular diseases and cancer that lead to premature mortality. This would yield higher social costs than IQ decrement alone . We disregarded for instance, drug costs and medical intervention costs such as intravenous chelation. Among other costs, the pretium doloris calculated on the basis of €8,000 per child in the Metal Blanc judgment was certainly underestimated, because only a small part of the children have been compensated, while also neglecting the psychological and economic suffering of the family or household of the children affected. We also estimated the need for special education to be 10% for children with B-Pb ≥ 100 μg/L. The somewhat uncertain data on crime costs suggest that the economic impact is comparatively low, but the costs of crime and rape were probably underestimated, because they did not include the value of statistical life, which may be greater than that of accidents (between €1999 0.5 to 1.5 million in Europe and French estimations were the lowest bracket estimate) [57, 58].
They highlight the additional social consequences of lead pollution. In regard to annual costs to invest in pollution abatement, our preliminary estimates are affected by the paucity of available data. We could not make a complete CBA because of lack of available data on the abatement costs, we had a very small part of the industrial costs. Official data from the ministry of Environment show that the major industrial sources of lead in France are the metals and non metallic minerals sectors . Three quarters of the 2007 emissions took place through water, and two waste treatment facilities alone amounted to 60% of total emissions of the ten most emitting facilities . We had also quite imprecise cost estimates for substitution of lead pipes, whose yearly estimates are certainly exaggerated. So far, clean-up costs of industrial lead-contaminated sites cannot be evaluated in France. Partial data stem from the experience of the highly polluted MetalEurop site remediated by SITA-Suez Environment, which amounted to €28 million . Unfortunately, these findings cannot be extrapolated to the national situation. As to contaminated sites, we point out the need for a specific evaluation. However, costs to decontaminate French houses with lead-based paint were available. And we calculated these costs once-for-all in one year, even if we overestimated the annual expenses, they appeared to be the most important efforts to be made in order to control the hazard. We could express an equivalent annual cost by using the capital recovery factor of standard interest calculations for loans which is the appropriate conversion factor. However, uncertainties remain regarding the time horizon and the social discount rate to use. A 0.05 conversion factor between one-time cost and annual cost is a compromise.
Some of the costs were paid within one year or paid over no more than five years, costs would be substantially less subsequent to that, while benefits would continue to accrue for each new birth cohort being born during the following years.
Our first estimates of total net benefit induced by reducing exposure to soils and dust in respect of the costs incurred by the decontamination of French houses with lead-based paint highlight that policies aimed at reducing lead exposures had an overall positive societal and economic impact. Additional estimates of total net benefit were performed, that considered the costs associated with dust and soils and drinking water lead pipes substitution. The expected health gains, according to the different B-Pb hypothetical threshold values, were calculated to be € 3.9 to 4 billion, € 1.86-2 billion and €0.12-0.25 billion respectively. The corresponding figures per child range from €1,661 to €1,721, €2,666 to €2,861, and €21,939 to €47,815, respectively. These estimates should be considered with caution, because of the uncertainty in the quality of data on costs of lead water pipes removal; a specific evaluation is also needed here.
Various uncertainties exist in our calculations: benefits linked to the dose-response function, and monetary valuation of the abatement costs linked to houses remediation, which yield uncertainties in the partial cost benefit estimates. According to Rabl and colleagues, there is a factor two uncertainty, both in the dose-response function and in the monetary valuation [62, 63]. Should the scientific literature show some day evidence of lower toxicity level values than the one we used in this sensitivity analysis, the health cost figures would be substantially increased.
The overall return of investments is important and must be taken into account by the policy makers. They are in line with several US findings that illustrate how reduction of childhood lead exposure has a high social benefit, in particular the studies from Schwartz , Salkever  and Grosse and colleagues . Between 1976 and 1999, Grosse et al.  estimated the economic impact of the trend of reduced lead exposure over 25 years in a cohort of children starting at 2 years of age in 2000. The estimate cost was valued from $110 to $319 billion (US) for the cohort each year, comparing it as if the blood lead concentration were that same as in 1975. Landrigan et al.  estimated the total annual costs of childhood lead poisoning to be $199743 billion in each birth cohort exposed to lead in the US. Their methodological approach was based on the contribution of environmental pollutants by using an Environmentally Attributable Fraction (EAF) model, which was estimated at 100% for lead poisoning. Recent studies calculated the economic impact of childhood poisoning below100 μg/L. The most recent major U.S. study was that of Gould . It was more comprehensive than those previously published, and produced a CBA by comparing the estimated costs in 1996 related to cleanup of lead-containing paint in the U.S. ($ 1 - $11 billion (US)) and secondly, by calculating the monetary benefits and social benefits by reducing lead exposure for a cohort of children <6 years ($192 - $270 billion) with earning losses amounted to 87% of total avoided costs. Total net benefits amounted to $ 181 - $ 269 billion. Therefore, a specific calculation induced by lead-based paint was not performed in this study. Muennig et al. , whereas, provided information on the benefits that might be realized if all children in the United States had a blood lead level of less than 10 μg/L. The net societal benefits showed improvements in high school graduation rates and reductions in crime would amount to $50,000 (SD, $14,000) per child annually at a discount rate of 3%. This would result in overall savings of approximately $1.2 trillion (SD, $341 billion) and produce an additional 4.8 million QALYs (SD, 2 million QALYs) for the US society as a whole.
Researchers in other European countries with prevalence of lead exposures similar to French figures may use this as a guide as to undertake similar economic assessments. Additionally, these data may motivate the revision of the current French policies as to whether or not to intervene in regard to lead pollution, and, in a more general sense, revamping France's overall policy on reducing pollution that may be affecting children's development. The introduction of unleaded petrol has greatly decreased emissions of lead in the atmosphere in France and globally. (Paris ambient air concentrations decreased by 97% between 1991 and 2005). The relative benefits of this action were substantial  and likely much greater than the benefits from further reduction of B-Pb levels today. Nonetheless, much abatement remains to be done, as other sources are only slowly being removed, if at all. The screening of houses for sale or rent with lead-based paint was implemented through the 2004 Public Health Act and its stringent policies on industrial emissions were triggered by EU regulations. The French 2004 national environmental health action plan has also contributed to the steady decrease in exposure of the general population and of its most vulnerable young segment over the last years in France.
EFSA recommends that "work should continue to reduce exposure to lead, from both dietary and non-dietary sources" . The major prevention campaigns aim to reduce lead exposure to the lowest possible level in order to protect children and childbearing age women. The obtained benefits for exposure levels <100 μg/L in this study are in line with the EFSA recommendations. They are a first step evaluation which should be expanded and refined. Our results emphasize the substantial monetary advantages obtained from preventing losses of a few IQ points because of lead exposures among children. While 1-point change in Full Scale IQ score is within the standard error of an individual's single measurement, it may be highly significant on a population basis .