ORIGINAL RESEARCH * NOUVEAUTES EN RECHERCHE

Blood lead levels in children and pregnant women living near a lead-reclamation plant Patrick Levallois,*t MD, MSc, FRCPC; Michel Lavoie,*t MD, MSc; Lise Goulett§ MD, PhD; Albert J. Nantel,* MD, MSc; Suzanne Gingras,t MSc Objective: To determine the effect of lead contamination around a lead-reclamation plant on the blood lead levels of children and pregnant women living in the area. Design: Prevalence study. Setting: Residents living 150 m or less (high-exposure area), 151 to 400 m (intermediateexposure area) or 401 to 800 m (low-exposure area) southeast from the plant. Participants: All children aged 10 years or less and all pregnant women living in the designated area. Outcome measures: Correlation of venous blood lead levels with soil lead concentrations in the areas in which the subjects lived and with sociodemographic and behavioural factors. Main results: Of the estimated 57 pregnant women 38 (67%) participated: 20 were in the high-exposure area and 18 in the other two areas; their geometric mean blood lead levels were low (0.15 and 0.13 gmol/L respectively). Of the 625 eligible children 510 (82%) participated: 169 were in the high-exposure area, 179 in the intermediate-exposure area and 162 in the low-exposure area; their geometric mean lead levels were 0.43, 0.30 and 0.26 MmolIL respectively. Within each age group children in the high-exposure area had the highest levels. The mean levels for children aged 6 months to 5 years were 0.49, 0.35 and 0.28 Amol/L in the three areas respectively. Within each exposure group children aged 1 to 2 years had the highest levels. No potential confounding variables could explain the relation between blood lead level and soil lead concentration.Conclusions: The pregnant women's blood lead levels did not seem to be affected by exposure level, but the children's levels were primarily related to the soil lead concentration.

Objectif: Preciser l'effet de la contamination au plomb, dans les environs d'une usine de recuperation du plomb, sur les taux sanguins de plomb chez les enfants et les femmes enceintes du secteur. Conception: Etude de prevalence. Cadre: Les residents vivant a 150 m au maximum (zone de forte exposition), de 151 a 400 m (zone d'exposition moyenne) ou de 401 A 800 m (zone de faible exposition) au sud-est de l'usine. Participants: Tous les enfants ages de 10 ans ou moins et toutes les femmes enceintes vivant dans la region designee. Mesure des resultats: Correlation entre les concentrations veineuses de plomb et les From the *Centre de toxicologie du Que'bec, Sainte-Foy, Que., the departments of community health, tCentre hospitalier de l'universite Laval, Sainte-Foy, Que., and $H6pital du Haut-Richelieu, Saint-Jean, Que., and the §departement de Medecine sociale et preventive, Universite de Montreal, Montreal, Que.

Reprint requests to: Dr Patrick Levallois, Departement de sante communautaire, Centre hospitalier de l'Universite Laval, 2050, boul. Saint-Cyrille ouest, Sainte-Foy, QC GI V2K8 CAN MED ASSOC J 1991; 144 (7)

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concentrations de plomb dans le sol des regions ou les sujets ont vecu, avec certains facteurs socio-demographiques et comportementaux. Principaux resultats: D'un total estimatif de 57 femmes enceintes, 38 (67 %) ont participe: 20 vivaient dans la region a forte exposition et 18, dans les deux autres secteurs; la moyenne geometrique des concentrations de plomb dans le sang etait faible (0,15 et 0,3 ,umol/L respectivement). Des 625 enfants admissibles, 510 (82 %) ont participe: 169 vivaient dans la zone de forte exposition, 179 dans la zone d'exposition moyenne et 162 dans le secteur a faible exposition; les concentrations moyennes geometriques de plomb dans le sang etaient respectivement de 0,43, 0,30 et 0,26 ,umol/L. Dans chaque groupe d'age, les enfants de la zone a forte exposition affichaient les concentrations les plus elevees. Les taux moyens pour les enfants ages de 6 mois a 5 ans etaient respectivement de 0,49, 0,35 et 0,28 gmol/L dans les trois secteurs. A l'interieur de chaque groupe d'exposition, les concentrations les plus elevees se retrouvaient chez les enfants ages de 1 a 2 ans. Aucune variable portant potentiellement a confusion ne pouvait expliquer le rapport entre les taux de plomb dans le sang et les concentrations de plomb dans le sol. Conclusions: Les taux sanguins de plomb chez les femmes enceintes ne semblaient pas dependre du taux d'exposition, mais chez les enfants, les taux etaient d'abord fonction des concentrations de plomb dans le sol.

I norganic lead is one of the most ubiquitous toxic substances. It has been used since antiquity, but its use has increased exponentially during the 20th century.' The main sources of environmental lead contamination in Canada are industry, such as metal smelters and lead-recycling facilities, and exhaust from motor vehicles using leaded gasoline."2 The principal route of human exposure is ingestion of food contaminated by lead particles or dust.2 In young children exposed to contaminated soil or dust the hand-to-mouth route may account for a large amount of the lead intake.3 The threat of lead poisoning in children and pregnant women is a public health concern.45 Although lead's toxic properties have been known for centuries, only recently has the scientific community tackled this problem rigorously.6'7 The use of the blood lead level as an indicator of exposure allows the study of dose-response relations in populations living in a steady state and subsequently the identification of blood lead levels of concern.7 From recent prospective studies it is obvious that a level between 0.48 and 0.72 ,umol/L may impair the psychomotor development of young children.4'5'7'8 One of the objectives proposed by the US Public Health Service as part of a strategy to promote health and prevent disease was to reduce the prevalence rate of blood lead levels exceeding 0.72 ,umol/L among children aged 6 months to 5 years to no more than about 5%.9 Given that the fetus is even more sensitive to the toxic effects of lead, the maximum acceptable level in pregnant women should be 0.48 jAmol/L.4 In 1989 environmental lead contamination was discovered in a residential area surrounding a leadreclamation plant in a town in Quebec. We carried out a study to determine the effect of the contamination on the lead intake of the local population. We also investigated sources of exposure to lead in the 878

CAN MED ASSOC J 1991; 144 (7)

homes of children in whom elevated blood lead levels were found.

Methods The lead-reclamation plant is located in a residential area and had operated for 5 years before our investigation. The main activity of the plant is recovering lead plates from old batteries. No lead smelting is done on the site. Lead dust was produced when pieces of lead were stored and handled in the plant yard. This was the suspected source of the soil contamination. The study population comprised all children up to 10 years old and all pregnant women living within about 800 m southeast of the plant, where lead dust was most likely to have been carried by the wind. Children living in this area were identified by means of the June 1989 municipal census. A total of 625 children met the inclusion criteria. Pregnant women were invited to participate through their physicians and advertisements in local newspapers and on radio stations. Exposure was classified according to the distance downwind from the plant. People living within about 150 m of the plant were considered to have a high level of exposure, those living 151 to 400 m from it an intermediate level of exposure and those living more than 400 m from it a low level of exposure. These categories were determined through preliminary measurements of soil lead concentration by the Ministere de l'environnement du Quebec (Francis Perron: personal communication, 1990). The top 2 cm of soil was collected under the porch and outside staircase of the residences. The median lead concentrations and the proportions of samples with a concentration above 600 parts per million (ppm) are shown in Table 1.

Blood samples were collected by means of venipuncture in 3-mL pediatric Vacutainer tubes (Becton-Dickinson, Mountainview, Calif.) proven to contain less than 0.01 ,umol/L of lead. The samples were stored at 4°C and transported within 24 hours to the Centre de toxicologie du Quebec, Sainte-Foy, for analysis. The blood lead level was determined by means of flameless atomic absorption spectrophotometry according to the method of Fernandez'0 with a Perkin-Elmer 5000 (Perkin-Elmer Corporation, Norwalk, Conn.) or Spectra-30 (Varian Instrument Group, Palo Alto, Calif.) instrument. Rigorous quality-control protocols were observed for determination of blood lead levels. The accuracy of the procedure was verified through the laboratory's participation in the Toxicology Blood Lead Proficiency Testing Program of the US Centers for Disease Control (CDC), Atlanta.'""2 All the results submitted to the CDC during the study period obtained an excellent rating. The reproducibility of the procedure was determined with two reference specimens (lead concentrations of 0.34 and 1.16 ,mol/L), which were reanalysed with each series of 10 study blood samples. The coefficients of variation for the two specimens were 10.6% (n = 64) and 5.7% (n = 63) respectively with the PerkinElmer instrument and 8.1% (n = 29) and 5.0% (n = 27) respectively with the Varian instrument. Duplicate analyses were also done on 10% of the study blood samples; the mean difference between the two samples was not significant (t = 0.54, p = 0.59 by paired t-testing). For children information was collected during a home interview with a parent on sociodemographic characteristics of the family, the child's behaviour, possible parental occupational exposure to lead, tobacco use in the family and age of the residence. The interviews were conducted from Sept. 1 to 19, 1989, by a group of nurses specifically trained to use a standardized questionnaire. Within a week after the interview the children were seen at a special clinic for blood collection. For pregnant women information was collected by means of a questionnaire on sociodemographic characteristics, possible

occupational exposure to lead, stage of the pregnancy, health problems during the pregnancy and tobacco use. Blood collection and the interview took place at the same clinic and during the same period as for the children. Medical evaluation and investigation of the home was done for children whose blood lead level was 0.97 ,mol/L or more. This level was chosen because it is the lower limit recommended by the Federal/Provincial Task Force on Acceptable Levels of Lead in Human Blood in 1987.'3 Medical evaluation was done by a pediatrician and consisted of a clinical examination to look for symptoms and signs of lead poisoning and determination of the hematocrit and the hemoglobin and free erythrocyte protoporphyrin (FEP) levels, as measured with a hematofluorometer (Aviv Biomedical Inc., Lakewood, NJ). Investigation of the home consisted of a detailed interview with the parents and lead sampling to identify most of the sources of potential exposure: house dust, tap water and interior house paint. Dust samples were collected from three sites (the top of furniture in the living room or child's bedroom, the kitchen floor and an indoor windowsill) by wiping a surface measuring 1000 cm2 with a preweighed piece of tissue paper.'4 The paper was reweighed and then soaked in 10% nitric acid for 1 hour. The available lead in the acid solution was measured by means of flame atomic absorption spectrophotometry. A 250-mL sample of tap water was taken from the first draw of the day from the cold water faucet in the kitchen. The lead concentration of interior paint chips was measured by means of flame atomic absorption spectrophotometry of a digested sample measuring 1 cm2 taken from a window frame or wall. The data were analysed with the Statistical Analysis System (SAS) for microcomputers.'5 Given the asymmetric distribution of blood lead levels we computed geometric means and geometric standard deviations.'6 We computed 95% confidence intervals (CIs) for the geometric means to compare exposure groups.'7 We used a global x2 test to compare the characteristics of the exposure groups, a test for trends to compare the blood lead levels and one-way

Table 1: Soil lead concentration in the vicinity of a lead-reclamation plant by level of exposure Level of exposure Intermediate High 118 104

Variable No. of samples Lead level, parts per million (ppm)

Range

Median % of samples with level above 600 ppm

Blood lead levels in children and pregnant women living near a lead-reclamation plant.

To determine the effect of lead contamination around a lead-reclamation plant on the blood lead levels of children and pregnant women living in the ar...
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