Three Decades of Lead Poisoning Prevalence in Mexico City Children: 1988 to 2015

Abstract

Epidemiologic studies may be the best approach to estimate lead exposure of the general population in countries where there is no national surveillance of blood lead levels (BLL). The United States Centers for Disease Control and Prevention (CDC) established in 2012 a reference level of 5 µg/dL to identify children with elevated BLL which represents the 97.5 percentile of children ages 1-5 years.We used data from five birth cohorts from the same health services in Mexico City, including the Early Life Exposure in Mexico and Environmental Toxicants (ELEMENT, 4 distinct studies), that enrolled children and mothers and followed them longitudinally. We estimated the time trends in the prevalence of Mexico City children with BLL ≥ 5 µg/dL. We focused on BLL of children 1 to 5 years old between 1988 and 2015. A total of 2,562 children contributed with 7,557 samples, with a maximum of one sample per child per year.The median blood lead levels decreased from 14.5 µg/dL in 1988 to 1.6 µg/dL in 2015. In 1988 the prevalence of children with BLL ≥ 5 µg/dL was 100%. In 1997, when lead was completely eliminated from the gasoline in Mexico City, it was 86.3% and ten years later, in 2007, 32.8%. In the period from 2010 to 2015 the prevalence fluctuated between 10.8% and 4.2%, suggesting that the decline has plateaued.30 years after eliminating leaded gasoline, remarkable progress has been made in reducing childhood lead poisoning, but there is still a high prevalence of children in Mexico City with elevated blood lead levels. Further public health interventions as well as a surveillance program are needed in order to further reduce lead, provide national estimates of blood lead levels in Mexico and to identify sources of exposure.