title: Differential association of lead on length by zinc status in two-year old Mexican children.
abstract: BACKGROUND
  Blood lead levels have decreased in Mexico since leaded fuel was banned in 1997, but other sources remain, including the use of lead-glazed ceramics for food storage and preparation. Zinc deficiency is present in almost 30% of children aged 1-2 years. Previous studies have documented negative associations of both lead exposure and zinc deficiency with stature, but have not considered the joint effects. Given that the prevalence of stunting in pre-school aged children was 13.6% in 2012, the aim of this study was to evaluate if the relationship between blood lead and child stature was modified by zinc status.
  
  
  METHODS
  Anthropometry, dietary energy intake, serum zinc and blood lead were measured in 291 children aged 24 months from an ongoing birth cohort study in Mexico City. Child stature was represented by recumbent length as appropriate for this age group. The association between blood lead (BPb) and length-for-age Z score (LAZ) was evaluated using a model stratified by zinc status measured by standard criteria and adjusted for: birth length, breastfeeding practices, energy intake, maternal height and education.
  
  
  RESULTS
  Median (IQR) BPb was: 0.17 (0.12-0.26) μmol/L and 17% of the sample had zinc deficiency (<9.9 μmol/L). BPb was inversely associated with LAZ in the overall sample (β = -0.19, p = 0.02). In stratified models, this negative association was more than three times higher and statistically significant only in the zinc deficient group (β = -0.43, p = 0.04) compared to the zinc replete group (β = -0.12, p = 0.22) (BPb*zinc status, p-for-interaction = 0.04).
  
  
  CONCLUSIONS
  Zinc adequacy is a key factor that may attenuate the negative association of lead on stature in young children.
authors.affiliation: Research Center for Nutrition and Health, National Institute of Public Health, Universidad No. 655 Colonia Santa María Ahuacatitlán, Cerrada Los Pinos y Caminera, C.P. 62100, Cuernavaca, Mor, Mexico. alejandra.cantoral@insp.mx.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Cantoral
authors.affiliation: Research Center for Nutrition and Health, National Institute of Public Health, Universidad No. 655 Colonia Santa María Ahuacatitlán, Cerrada Los Pinos y Caminera, C.P. 62100, Cuernavaca, Mor, Mexico. mmtellez@insp.mx.
authors.forename: Martha M
authors.initials: MM
authors.lastname: Téllez-Rojo
authors.affiliation: Research Center for Nutrition and Health, National Institute of Public Health, Universidad No. 655 Colonia Santa María Ahuacatitlán, Cerrada Los Pinos y Caminera, C.P. 62100, Cuernavaca, Mor, Mexico. tshamah@insp.mx.
authors.forename: Teresa Shamah
authors.initials: TS
authors.lastname: Levy
authors.affiliation: National Institute of Public Health, Universidad No. 655, Colonia Santa María Ahuacatitlán, Cerrada Los Pinos y Caminera, C.P. 62100, Cuernavaca, Mor, Mexico. mhernan@insp.mx.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Hernández-Ávila
authors.affiliation: National Institute of Perinatology, Monte Urales Sur 800, Lomas Virreyes, C.P. 11000, Mexico City, Mexico. lschnaas@hotmail.com.
authors.forename: Lourdes
authors.initials: L
authors.lastname: Schnaas
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, 155 College St, 6th floor, Toronto, ON, M5T 3M7, Canada. howard.hu@utoronto.ca.|Department of Nutritional Sciences, University of Michigan School of Public Health, 1415 Washington Heights, Ann Arbor, MI, 48104, USA. howard.hu@utoronto.ca.
authors.forename: Howard
authors.initials: H
authors.lastname: Hu
authors.affiliation: Department of Nutritional Sciences, University of Michigan School of Public Health, 1415 Washington Heights, Ann Arbor, MI, 48104, USA. karenep@umich.edu.|Department of Nutrition, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA, 02215, USA. karenep@umich.edu.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Peterson
authors.affiliation: Department of Nutritional Sciences, University of Michigan School of Public Health, 1415 Washington Heights, Ann Arbor, MI, 48104, USA. adrienne.ettinger@gmail.com.
authors.forename: Adrienne S
authors.initials: AS
authors.lastname: Ettinger
mesh_terms: D001827:Body Height; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004781:Environmental Exposure / Q000009:adverse effects*; D004785:Environmental Pollutants / Q000097:blood / Q000633:toxicity*; D005260:Female; D006130:Growth Disorders / Q000097:blood / Q000175:diagnosis / Q000209:etiology*; D006801:Humans; D007854:Lead / Q000097:blood / Q000633:toxicity*; D016014:Linear Models; D008297:Male; D008800:Mexico; D014131:Trace Elements / Q000097:blood / Q000172:deficiency*; D015032:Zinc / Q000097:blood / Q000172:deficiency*
chemical_list: D004785:Environmental Pollutants; D014131:Trace Elements; D007854:Lead; D015032:Zinc