Lead contamination in Uruguay: the "La Teja" neighborhood case

Lead, ubiquitous in the environment as a result of mining and industrialization, is found as a contaminant in humans although it has no known physiological function there. Lead-exposed children are known to be the population with the highest potential health risks. The recommended biomarker to assess environmental lead exposure in animals is lead level in blood. Before 2001, the Department of Toxicology and Environmental Hygiene was the only team to produce human monitoring data on Uruguayan populations (Manay 2001a,b; Mañay et al. 1999). Lead pollution in Uruguay first received official attention during the 2001 La Teja poisoning episode. It was in the La Teja neighbourhood of Montevideo that high BLL were found in children (as high as 20 microg/dL), prompting corrective responses from Health and Environmental authorities. Growing awareness of environmental lead pollution and consequential human health effects from that event, resulted in public debate and demands for solutions from Health and Environmental authorities. Citizens demanded public disclosure of information concerning lead pollution and wanted action to address contaminated Uruguayan sites. In response, the Ministry of Health assembled an interinstitutional multidisciplinary committee, with delegates from health, environmental, labor, educational, and social security authorities, as well as community nongovernmental organizations (NGOs), among others. The University of the Republic was designated to serve as the main responsible entity for technical advice and support. After 2001, new research on lead pollution was undertaken and included multidisciplinary studies with communities in response to health risk alerts. The main emphasis was placed on children exposed to environmental lead. Major sources of Uruguayan lead contamination, similar to those in other developing countries, result from metallurgical industries, lead-acid battery processing, lead wire and pipe factories, metal foundries, metal recyclers, leaded gasoline (before December 2003), lead water pipes in old houses, and scrap and smelter solid wastes, among others. Nonoccupational lead exposure usually results from living in or near current or former manufacturing areas or improper handling of lead-containing materials or solid wastes (a particularly important health risk for children). In this chapter, we reviewed available studies published or reported after the pollution events first announced in 2001. These studies include data on exposure, health, and actions taken to mitigate or prevent lead exposure from pollution events in Uruguay. Uruguay adopted CDC's 10 microg/dL as the reference BLL for children (CDC 1991) and a BLL of 30 microg/dL for workers (from the ACGIH standard). Environmental authorities adopted the Canadian reference concentrations for soil: residential and playgrounds (> 140 mg/kg) or industrial areas (> 600 mg/kg) (CCME 2006). Most studies reviewed addressed soil pollution as the main source of lead exposure. Results of thousands of analyses indicated that most children had BLL above reference intervention limits. A significant decrease in BLL was also found over time in the study results, demonstrating the importance of medical intervention, nutrition, and environmental education. The severity of lead pollution discovered required official governmental actions, both to reduce sources of lead contamination and to address the health implications for children who had been exposed to environmental or industrial lead pollution. Dogs were discovered to be useful sentinels for environmental lead pollution; they had higher BLL than children when exposed to the same polluted environment and developed symptoms of lead intoxication earlier and at lower BLL than did children. This same pattern was also observed in families with children and pet dogs living in the La Teja neighborhood. This discovery renders dogs prospectively useful in lead pollution monitoring and diagnosis, particularly in developing countries. BLL results from similar human lead exposure studies conducted 10 yr apart showed significant BLL reductions, after 10 yr, for nonoccupationally exposed Uruguayans. The phase-out of leaded gasoline is thought to have contributed to this improvement. New laws to address occupational and environmental exposures were passed to prevent new cases of lead contamination, and new research studies are underway to monitor lead pollution. Moreover, a systematic surveillance screening program for lead workers and children is planned, although it is not yet underway. The sensitization of the public to the lead pollution problem has been a key driver of governmental action to mitigate and prevent further lead pollution in Uruguay. The changes made since 2001 appear to have yielded positive results. BLL from different populations studied more recently show decreased lead levels, suggesting a lower contribution of environmental lead to exposure of children and nonoccupationally exposed adults. The diverse analytical data collected on lead pollution in Uruguay between 2001 and 2004 were the main ingredient that allowed effective identification of lead pollution in Uruguay and paved the way for official intervention to prevent new pollution events. Nevertheless, full research studies must still be done, including both spot analysis of environmental soil, air, and water samples, and extensive screening of BLL. Future health and environmental actions are needed, not only to remediate known areas of lead pollution, but also to investigate other sources of potential health risks.