Children's Blood Lead Concentrations from 1988 to 2015 in Mexico City: The Contribution of Lead in Air and Traditional Lead-Glazed Ceramics

Abstract

Despite the removal of lead from gasoline in 1997, elevated blood lead levels (BLLs) > 5 µg/dL are still detectable in children living in Mexico City. The use of lead-glazed ceramics may explain these persistent exposure levels. Mexico lacks a national surveillance program for BLL, but temporal trends can be derived from epidemiological studies. With this approach, we leveraged a series of birth cohorts to report BLL trends from 1987 to 2002 and expanded our analysis to 2015. Data were from 1⁻5-year-old children from five Mexico City cohorts followed between 1988 and 2015. BLLs are reported on 1963 children, who contributed 4975 BLLs. We estimated the trend of mean BLL, which decreased from 15.7 µg/dL in 1988, to 7.8 µg/dL in 1998 (a year after the total ban of lead in gasoline), to 1.96 µg/dL in 2015. The proportion of BLL ≥ 5 µg/dL decreased from 92% (1988⁻1998) to 8% (2008⁻2015). The use of lead-glazed ceramics was associated with an 11% increase in BLLs throughout the study period. Replacing lead-based glazes in traditional ceramics may be the key to further reducing exposure, but this presents challenges, as it involves a cultural tradition deeply rooted in Mexico. In addition, the creation of a rigorous, standardized, and on-going surveillance program of BLL is necessary for identifying vulnerable populations.

Keywords: Mexico City cohorts; children’s blood lead; lead in air; lead-glazed ceramics.

Figure 1

Percent of children with lead in blood concentrations higher than 5 µg/dL for each age group and cohort.

Figure 2

Contribution of lead in air on blood lead levels at each age. The 5-year slope of air lead on blood lead was significantly higher than the 1-year slope.

Figure 3

Results of adjusted mixed models for blood lead concentrations and air lead concentrations over the years. 1 = 1990: Introduction of “Magna Sin” (reduced lead) gasoline and one day a week without driving your car program. 2 = 1991: Closure of oil refinery in Mexico City (Azcapotzalco). Reduction to 0.5–1 mL/gal of tetraethyl lead in gasoline. 3 = 1992: Reduction to 0.2–0.3 mL/gal of tetraethyl lead in gasoline. 4 = 1994: Reduction to 0.1–0.2 mL/gal of tetraethyl lead in gasoline. 5 = 1997: Lead completely phased out of gasoline. 2014 and 2015 air lead levels were extrapolated from the 2013 air lead levels due to lead in air no longer being measured after 2013.