Lead-glazed ceramic ware and blood lead levels of children in the city of Oaxaca, Mexico

Although Mexico substantially reduced use of leaded gasoline during the 1990s, lead-glazed pottery remains a significant source of population exposure. Most previous studies of lead in nonoccupationally exposed groups in Mexico have been conducted in the Mexico City metropolitan area. Oaxaca, a poor southern state of Mexico, has a centuries-old tradition of use of low temperature lead-glazed ceramic ware manufactured mainly by small family businesses. We measured blood lead levels in 220 8-10-y-old children (i.e., not from pottery-making families) who were students in the innercity of Oaxaca and in the mothers of all children. The geometric mean blood lead level of the children was 10.5 microg/dl (+7.0/-4.3 microg/dl standard deviation; range = 1.3-35.5 microg/dl). The corresponding mean value for the mothers was 13.4 (+9.0/-5.4 microg/dl standard deviation; range = 2.8-45.3 microg/dl). We used cutoffs that were greater than or equal to 10 microg/dl, 20 microg/dl, and 30 microg/dl, and we determined that 54.9%, 10.3%, and 3.0% of the children were at or above the respective criteria. We accounted for 25.2% of the variance in blood lead levels of the children, using maternal responses to a questionnaire that assessed possible lead sources in a linear multiple-regression model. The most important factors related to lead levels were family use of lead-glazed pottery, use of animal fat in cooking, and family income. The addition of maternal blood lead level to the model increased accounted variance in blood lead to 48.0%. In logistic-regression modeling of children's blood lead levels, we used a cutoff of greater than or equal to 10 microg/dl, and we found that use of lead-glazed pottery was the most important of all questionnaire items that were predictive of blood lead levels (odds ratio = 2.98). In Oaxaca, as is the case elsewhere in Mexico, lead-glazed ceramic ware remains a significant risk factor for elevated blood lead levels in children.     

Blood Lead Secular Trend in a Cohort of Children in Mexico City. II. 1990–1995

The authors determined the secular trend in blood lead levels in a cohort of 91 children born in Mexico City between 1987 and the beginning of 1993. The authors grouped children by calendar year in which they reached 36 mo of age (i.e., 1990–1995), and their blood lead levels were measured every 6 mo during a 66-mo period. The overall geometric mean blood lead level was 8.6 μmlg/dl (range = 1.0–61.0 μmlg/dl). A repeated measures analysis of variance revealed a significant downward linear trend in blood lead levels by year (p < .001)—from an estimated marginal geometric mean of 14.2 μmlg/dl in 1990 to 6.3 μmlg/dl in 1995. There was also a significant linear age effect (p < .001); blood lead levels generally fell during the 36th-66th mo. Family use of lead-glazed pottery significantly elevated blood lead levels (p = .006), and the effect magnified as age increased (Age x Pottery Interaction [p = .014]). Although the overall downward trend in blood lead levels during the time period described corresponded to a reduction in various sources of lead exposure, there was no alteration in production, distribution, or use of leaded pottery. Currently, use of lead-glazed ceramic pottery is one of the most profound sources of lead exposure in the Mexican population.     

Blood lead secular trend in a cohort of children in Mexico City. II. 1990-1995

The authors determined the secular trend in blood lead levels in a cohort of 91 children born in Mexico City between 1987 and the beginning of 1993. The authors grouped children by calendar year in which they reached 36 mo of age (i.e., 1990-1995), and their blood lead levels were measured every 6 mo during a 66-mo period. The overall geometric mean blood lead level was 8.6 microg/dl (range = 1.0-61.0 microg/dl). A repeated measures analysis of variance revealed a significant downward linear trend in blood lead levels by year (p < .001)--from an estimated marginal geometric mean of 14.2 microg/dl in 1990 to 6.3 microg/dl in 1995. There was also a significant linear age effect (p < .001); blood lead levels generally fell during the 36th-66th mo. Family use of lead-glazed pottery significantly elevated blood lead levels (p = .006), and the effect magnified as age increased (Age x Pottery Interaction [p = .014]). Although the overall downward trend in blood lead levels during the time period described corresponded to a reduction in various sources of lead exposure, there was no alteration in production, distribution, or use of leaded pottery. Currently, use of lead-glazed ceramic pottery is one of the most profound sources of lead exposure in the Mexican population.     

Factors associated with lead exposure in Oaxaca,Mexico

Lead intoxication risks were studied in a community of ceramic folk art workers in Oaxaca, a southern state of Mexico, where the manufacture of low-temperature lead ceramic ware is a family tradition and often the only source of income. Variables such as household characteristics, occupation, and lead exposure risk factors were explored. Study participants' mean blood lead concentration was 43.8 microg/dl (range=8.4-99.6 microg/dl), which is over the WHO guideline of 40 microg/dl for removing workers from exposure and is the concentration over which renal damage is accelerated. Best predictors for high blood lead concentrations by multivariable regression analysis were: occupation (P<0.0001), gender (P=0.0002), and the use of glazed stoneware (P<0.0001). This model explained 18% of blood lead variation among the study group. Exposure appears to be primarily associated with antiquated pottery manufacturing techniques and the high degree of contamination prevailing at the production sites, which in most cases are their living quarters. This consequently affects the lead levels of the entire community.     

Editorial: The Bhopal Gas Disaster: It's Not Too Late for Sound Epidemiology

In Russia, hair, rather than blood, is usually used as a substrate for screening children for lead poisoning. We attempted to gauge the accuracy of this method by comparing these two methods. The evaluation was done in Saratov, Russia. We collected hair and blood samples from 189 children who attended 11 kindergartens. Their mean blood lead concentration was 9.8 μmlg/dl (range = 3.1–35.7 μmlg/dl), and their mean hair lead concentration was 7.2 μmlg/g (range = 1.0–7.2 μmlg/g [i.e., 1.0 being the lowest detectable limit]). Hair lead concentration as a screening method had 57% sensitivity and resulted in 18% of the children being classified as false-negatives. We conclude, therefore, that measuring hair lead concentration is not an adequate method with which to screen children for lead poisoning.     

Variation in Blood Lead and Hematocrit Levels during Pregnancy in a Socioeconomically Disadvantaged Population

Lead is a long-recognized human toxicant that crosses the placenta. Fetal sensitivity to environmental agents can vary with stage of development; therefore, how maternal blood lead levels change during pregnancy and how fetal exposure is influenced provide useful knowledge. In this study, the authors describe longitudinal changes in blood lead levels during the course of pregnancy in a sample of socioeconomically disadvantaged pregnant women. The women were recruited early in pregnancy when they sought care at one of two obstetrics clinics in Albany, New York. Maternal blood lead levels changed between the 1st and 2nd trimesters, from 1.99 μmlg/dl to 1.69 μmlg/dl (hematocrit corrected, 1.70–1.62); between the 2nd and 3rd trimester from 1.78 μmlg/dl to 1.86 μmlg/dl (hematocrit corrected, 1.65–1.72); and between 3rd trimester and delivery from 1.80 μmlg/dl to 2.17 μmlg/dl (hematocrit corrected, 1.70–1.86). These changes were statistically significant and were corrected for secular trends. The rate of change per day in lead levels averaged ?36.6% from trimester 1 to trimester 2, 18.3% from trimester 2 to trimester 3, and ?40.8% from trimester 3 to delivery. The patterns in our study were consistent with the patterns reported in a few other longitudinal studies of change in lead level during pregnancy. Findings reveal significant associations between maternal blood lead levels and both hematocrit and trimester of pregnancy. Clinicians who interpret test results should take into account the dynamics of these variables when determining appropriate care for both mother and neonate.     

Blood lead secular trend in a cohort of children in Mexico City (1987-2002)

We determined the secular trend in blood lead levels in a cohort of 321 children born in Mexico City between 1987 and 1992. Blood lead level was measured every 6 months during a 10-year period. We modeled the effect of yearly air lead concentration nested within the calendar year in which the child was born, family use of lead-glazed pottery, socioeconomic status, year in which the child was born, age of the child at the time of blood lead measurement, place of residence, and an indicator variable for subjects with complete or incomplete blood lead values. The yearly mean of air lead of the Valley of Mexico decreased from its highest level of 2.80 microg/m3 in 1987 to 0.07 microg/m3 in 2002. The contribution of air lead to blood lead according to year of birth was strongest for subjects born in 1987 and fell to nearly zero for children born in 1992. The geometric mean of the entire cohort rose from 8.4 microg/dL in the first year of life to 10.1 microg/dL in the second and decreased thereafter until it reached 6.4 microg/dL at 10 years of age. Children of families who used lead-glazed ceramics had blood lead levels 18.5% higher than did children of nonusing families. Children who belonged to the lowest socioeconomic levels had blood lead levels 32.2% higher than did those of highest socioeconomic levels. Children who lived in the northeast part of the city had blood lead levels 10.9% higher compared with those who lived in the southwest.     

Environmental urban lead exposure and blood lead levels in children of Mexico City.

Lead contamination is now a leading public health problem in Mexico. However, there are few data on the lead content of various environmental sources, and little is known about the contribution of these sources to the total lead exposure in the population of children residing in Mexico City. We conducted a cross-sectional study in a random sample of 200 children younger than 5 years of age who lived in one of two areas of Mexico City. Environmental samples of floor, window, and street dust, paint, soil, water, and glazed ceramics were obtained from the participants' households, as well as blood samples and dirt from the hands of the children. Blood lead levels ranged from 1 to 31 micrograms/dl with a mean of 9.9 micrograms/dl (SD 5.8 micrograms/dl). Forty-four percent of the children 18 months of age or older had blood lead levels exceeding 10 micrograms/dl. The lead content of environmental samples was low, except in glazed ceramic. The major predictors of blood lead levels were the lead content of the glazed ceramics used to prepare children's food, exposure to airborne lead due to vehicular emission, and the lead content of the dirt from the children's hands. We conclude that the major sources of lead exposure in Mexico City could be controlled by adequate public health programs to reinforce the use of unleaded gasoline and to encourage production and use of unleaded cookware instead of lead-glazed ceramics.     

Different Associations of Blood Lead,Meso 2,3-Dimercaptosuccinic Acid (DMSA)-Chelatable Lead,and Tibial Lead Levels with Blood Pressure in 543 Former Organolead Manufacturing Workers

In this study, the authors' objective was to determine the influence of blood lead, meso 2,3-dimercaptosuccinic acid (DMSA)-chelatable lead, and tibial lead on systolic and diastolic blood pressures and on hypertension in 543 former organolead manufacturing workers. All workers had past exposure to inorganic and organic lead. The authors used linear regression to model systolic and diastolic blood pressure separately, and logistic regression was used for the modeling of hypertension status (i.e., systolic blood pressure > 160 mm Hg, diastolic blood pressure ≥ 96 mm Hg, or current use of antihypertensive medications). Blood lead, DMSA-chelatable lead, and tibial lead levels had means (standard deviations appear within parentheses) of 4.6 μmlg/dl (2.6 μmlg/dl), 19.3 μmlg (17.2 μmlg), and 14.4 μmlg/g (9.3 μmlg/g) respectively. The authors adjusted for covariates, and they found that blood lead was a predictor of (1) both systolic and diastolic blood pressures and (2) hypertension status in men ≤ 58 y of age. DMSA-chelatable lead and tibial lead were not associated with any of the blood pressure measures. Systolic blood pressure was elevated by blood lead levels as low as 5 μmlg/dl. We speculate that lead may have a transient influence on blood pressure that is related to target dose levels obtained once release of lead from body stores has occurred.     

An assessment of lead leachability from lead-glazed ceramic cooking vessels

Since the early 1990s, numerous studies in Mexico have demonstrated an association between the use of lead-glazed ceramic cooking ware (LGC) and elevated blood lead levels. We sought to determine whether ceramic ware collected from the Hispanic community in Oklahoma City contained lead and to quantify the amount of lead that leached into foods cooked in those vessels. Lab results were combined with consumer intake levels for foods and compared with the provisional tolerable total intake level (PTTIL) for lead. The authors found that 52 percent of the vessels they tested exceeded the FDA action level for ceramic ware. Consumption of a low-pH food (tomatoes) cooked in 23 of 25 vessels would result in a dose of lead exceeding the PTTIL compared with 3 of 25 vessels and 5 of 25 vessels for a higher-pH foods (hominy and beans, respectively). The results of the study indicate that LGC is still used in the local community and represents a significant public health concern.     

Prevalence and determinants of lead intoxication in Mexican children of low socioeconomic status.

This paper reports on the prevalence of lead poisoning in children between 1 and 5 years of age living in a marginal area to the north of Mexico City and also includes an evaluation of sources of exposure to this metal in the same area. The results show that 67.5% of the children studied have blood lead (PbB) levels > or = 10 micrograms/100 ml. Twenty-one percent of these children (1987) had PbB levels that required medical evaluation (> or = 20 micrograms/100 ml- < or = 40 micrograms/100 ml), and 112 children needed medical treatment (PbB > or = 40 micrograms/100 ml). In addition, the study found that the probability of higher blood lead levels (> or = 20 micrograms/dl) corresponds to children whose mothers use lead-glazed pottery dishes (OR = 2.80; CI 95%, 1.55-5.07) and to children who habitually bite colored pencils (OR = 2.05; CI 95%, 1.13-3.71) compared, respectively, with children whose mothers do not use that type of dishes and children who do not bite pencils. Our results provide baseline information for estimating the impact and costs of population-based interventions aimed at these populations and also confirm the need to strengthen health education programs to promote the reduction of lead exposure in the general population.     

Impact of Soil and Dust Lead on Children's Blood Lead in Contaminated Areas of Sweden

The impact of lead in soil and dust on blood lead concentrations in young children (i.e., 1–5 y of age, N = 202) and the risk of health effects were investigated in an urban and a mining area of Sweden. Blood, soil, and indoor dust, as well as information on lead-exposure factors, were collected. The blood lead concentrations (total range = 9–77 μmlg/l) the authors measured indicated a low risk for lead-induced health effects. Lead in soil (i.e., < 10–5,000 μmlg/g) and in dust (i.e., < 1–316 μmlg/g) had little effect on blood lead concentrations, given the present conditions and present concentration range—especially in the mining area. Urban children had significantly higher blood lead concentrations than children in the mining area, despite higher concentrations of lead in soil in the mining area. In the urban children, blood lead concentrations were influenced by parental smoking and lead in dust at day-care centers.     

A rapid lead test: Public outreach and testing to detect leachable lead in ceramic ware

A modification of the U.S. Food and Drug Administration (FDA) lead screening test of ceramic ware was made to screen large numbers of samples in a short time frame. Ceramic ware in use by Davis and Sacramento, California residents was tested. Lead was leached from ceramic ware with citric acid and identified by rhodizonic acid in this quick, qualitative test. Of 92 individual pieces of pottery tested, approximately 6.6% were positive for leachable lead. Approximately 67% of the positive samples were handmade in Mexico. This rapid test is sensitive to two (2) parts per million (ppm, g/g) leachable lead. Ceramic ware with detectable leachable lead levels may present a health risk to individuals who habitually use such items for food storage and/or consumption. Because only 20–30 minutes is needed to perform the test, immediate communication of results to the participant is possible.     

Dietary and environmental determinants of blood and bone lead levels in lactating postpartum women living in Mexico City.

Despite the recent declines in environmental lead exposure in the United States and Mexico, the potential for delayed toxicity from bone lead stores remains a significant public health concern. Some evidence indicates that mobilization of lead from bone may be markedly enhanced during the increased bone turnover of pregnancy and lactation, resulting in lead exposure to the fetus and the breast-fed infant. We conducted a cross-sectional investigation of the interrelationships between environmental, dietary, and lifestyle histories, blood lead levels, and bone lead levels among 98 recently postpartum women living in Mexico City. Lead levels in the patella (representing trabecular bone) and tibia (representing cortical bone) were measured by K X-ray fluorescence (KXRF). Multivariate linear regression models showed that significant predictors of higher blood lead included a history of preparing or storing food in lead-glazed ceramic ware, lower milk consumption, and higher levels of lead in patella bone. A 34 micrograms/g increase in patella lead (from the medians of the lowest to the highest quartiles) was associated with an increase in blood lead of 2.4 micrograms/dl. Given the measurement error associated with KXRF and the extrapolation of lead burden from a single bone site, this contribution probably represents an underestimate of the influence of trabecular bone on blood lead. Significant predictors of bone lead in multivariate models included years living in Mexico City, lower consumption of high calcium content foods, and nonuse of calcium supplements for the patella and years living in Mexico City, older age, and lower calcium intake for tibia bone. Low consumption of milk and cheese, as compared to the highest consumption category (every day), was associated with an increase in tibia bone lead of 9.7 micrograms Pb/g bone mineral. The findings of this cross-sectional study suggest that patella bone is a significant contributor to blood lead during lactation and that consumption of high calcium content foods may protect against the accumulation of lead in bone.     

Determinants of bone and blood lead levels among teenagers living in urban areas with high lead exposure.

Although lead has been extensively studied in children, its sources and effects remain unclear in adolescents. This study examined the relation of blood and tibia bone lead levels to lead determinants. One hundred adolescents living in Mexico City and surrounding suburbs were studied. Blood lead was measured by atomic absorption spectroscopy, and tibia lead was measured by a K X-ray Fluorescence (KXRF) instrument. Blood lead ranged from 1.8 to 29.2 microgram/dl, with a mean of 7.4 microgram/dl. Bone lead ranged from <1 to 44.82 microgram Pb/g bone mineral, with a mean of 4.8 microgram Pb/g. Predictors of bone lead included higher traffic density near the home, mother's smoking history, and time spent outdoors. Predictors of log-transformed blood lead included bone lead levels, male sex, use of lead-glazed ceramics, and living in Mexico City. Bone lead remained a significant predictor of blood lead after adjusting for covariates in a final multivariate regression model. In our final model, a rise in bone lead from the middle of the lowest quintile to the middle of the highest quintile (a difference of 21.6 microgram Pb/g) was associated with an increase in blood lead of 1.2 microgram/dl. Our data suggest that in addition to current sources of environmental lead exposure, bone lead accumulated over time constitutes a moderate source of circulating lead during adolescence and may account for some of the adverse health effects documented in recent studies.     

Determinants of Blood Lead Levels across the Menopausal Transition

In this study, the authors sought to evaluate the impact of menopause on lead remobilization from bone-lead stores. The study was conducted between 1993 and 1995 in Mexico City and included 903 women (mean age = 46.8 y [standard deviation = 8.2 y]). Participants provided information about reproductive variables and known risk factors for high PbB levels. PbB levels were determined with graphite furnace atomic absorption spectrophotometry. The authors used linear-regression models to describe the relationship between PbB levels and variables of interest. PbB levels ranged from 1.0 μg/dl to 43.8 μg/dl (mean = 11.0 μg/dl). Menopausal women at baseline had the highest PbB levels; the mean difference between pre- and postmenopausal women was 0.76 μg/dl (95% confidence interval = 0.024, 1.48). We observed an inverted U-shaped relationship between PbB level and age. The highest PbB levels were observed in women aged 47-50 y. Other important predictors of PbB levels were use of lead-glazed ceramics, number of pregnancies, history of cigarette smoking, and height. Our results support the hypothesis that bone lead may be mobilized during menopause and may constitute an important source of exposure.     

Re-Examination of Longitudinal Studies of Workers

This cross-sectional study examined the association between blood lead levels and neuropsychological and behavioral development of 139 children (7–9 y of age) who attended school in the southwestern part of Mexico City. A trained psychologist administered an IQ test to 84% of the children, and teachers graded them for agility, socialization, expression, and knowledge. Parents also answered a questionnaire on demographic and socioeconomic variables. Anodic stripping voltametry was used to determine blood lead levels. Regression models were used to determine the best predictors of IQ and teachers' rating scores. The mean blood lead level was 19.4 μg/dl (standard deviation [SD] = 7.6), with a geometric mean of 17.8 μg/dl (95% confidence interval [95% CI] = 16.5–19.1). Blood lead was the strongest predictor of full-scale IQ, and there was a significant negative trend between blood lead, full-scale IQ, and teachers' rating scores. In this study, children with higher levels of blood lead performed more poorly on psychometric tests and had poorrer educational attainment than their counterparts. These results suggest an association between neuropsychological and behavioral impairment and lead exposure.     

Blood Lead Levels in Children in South Central Los Angeles

We retrospectively reviewed 3 679 pediatric records from King/Drew Medical Center, south central Los Angeles, between 1991 and 1994. Blood lead levels of children were followed to age 18 y. Patients were not referred specifically for lead poisoning. The sample was primarily Latino. Geometric mean blood lead peaked at 6.7 μg/dl (0.32 μmol/l) between 2 and 3 y of age. There was a downward secular trend and a seasonal trend. Males had higher lead levels than females. Children who lived in several zipcode areas, in which the lowest family incomes were reported, had higher lead levels. More Latino children had higher lead levels than African American children. Latino children (i.e., 20.2%) who were 1–5 y of age had blood lead levels that were ≤ 10 μg/dl. Young Latino children in this zone of Los Angeles may be at increased risk for lead exposure.     

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Risk factors associated with blood lead levels exceeding 15 μg/dl were analyzed in this report. This relatively high lead level was selected because, at the time the study commenced, it was considered to be a “safe” level. A total of 1 583 schoolchildren were studied. The students were from (a) two areas in Mexico City (Tlalnepantla and Xalostoc) that have had historically high concentrations of lead in air; and (b) three areas (Pedregal, Iztalpalapa, and Centra) with less impressive air lead levels. Parents were presented with a questionnaire that solicited information about lead risk factors. A bivariate analysis and a multilogistic analysis were conducted to identify associations and to identify the model that most accurately explains the variability of the sample. High blood lead concentrations were found in children who lived in Xalostoc and Tlalnepantla (16.1 and 17.0 μg/dl, respectively), and the lowest concentration (i.e., 10 μg/dl) was found in children from Iztapalapa. The strongest association was with area of residence, followed by education level of parents, cooking of meals in glazed pottery, and chewing or sucking of yellow or other colored pencils. A child's area of residence is the most significant risk factor that must be accounted for when any study of lead and blood lead concentrations is undertaken. Follow-up in similar populations should assist greatly in the evaluation of the impact of governmental actions on public health.     

Low-Level Lead Exposure and Blood Lead Levels in Children: A Cross-Sectional Survey

The authors studied 53 girls (44.5%) and 66 (55.5%) boys in Karachi, Pakistan, to determine their blood lead levels. The association between blood lead levels/water lead levels and the possible risk factors and symptoms associated with lead toxicity was explored. The mean lead level for the entire group was 7.9 μg/dl (standard deviation = 4.5 μg/dl). Thirty (25.2%) of the children had lead levels that exceeded 10 μg/dl; 12 (10.0%) of these had lead levels that exceeded 15 μg/dl. Thirteen (20.9%) of the children under the age of 6 yr (n = 62) had lead levels greater than 10 μg/dl, and 6 (9.6%) had levels in excess of 15 μg/dl. The authors found no association (p > .05) between high lead levels in water and blood lead levels in children. Mean blood lead levels were highest in the group of children exposed to various risk factors for lead absorption (e.g., exposure to paint, remodeling, and renovation; use of lead utensils; pica). There was a significant association between a history of exposure to paint/renovation activities and a history of pica. High blood lead levels in the children in Karachi stress the urgency for actions that control lead pollution. Screening programs should be instituted by the state. Individuals must become aware of lead's toxicity, and they must avoid substances that contain lead.