Predictors Of Blood Lead Levels Research Articles

A new approach to a legacy concern: Evaluating machine-learned Bayesian networks to predict childhood lead exposure risk from community water systems.

Lead in drinking water continues to put children at risk of irreversible neurological impairment. Understanding drinking water system characteristics that influence blood lead levels is needed to prevent ongoing exposures. This study sought to assess the relationship between children's blood lead levels and drinking water system characteristics using machine-learned Bayesian networks. Blood lead records from 2003 to 2017 for 40,742 children in Wake County, North Carolina were matched with the characteristics of 178 community water systems and sociodemographic characteristics of each child's neighborhood. Bayesian networks were machine-learned to evaluate the drinking water variables associated with blood lead levels ≥2μg/dL and ≥5μg/dL. The model was used to predict geographic areas and water utilities with increased lead exposure risk. Drinking water characteristics were not significantly associated with children's blood lead levels ≥5μg/dL but were important predictors of blood lead levels ≥2μg/dL. Whether 10% of water samples exceeded 2ppb of lead in the most recent year prior to the blood test was the most important water system predictor and increased the risk of blood lead levels ≥2μg/dL by 42%. The model achieved an area under the receiver operating characteristic curve of 0.792 (±0.8%) during ten-fold cross validation, indicating good predictive performance. Water system characteristics may thus be used to predict areas that are at risk of higher blood lead levels. Current drinking water regulatory thresholds for lead may be insufficient to detect the levels in drinking water associated with children's blood lead levels.

Lead in New York City's soils: Population growth, land use, and contamination.

Soil is an important exposure pathway for lead (Pb) and predictor of blood lead levels (BLL) among children. Over the past two decades, many areas within New York City (NYC) have undergone a transition from industrial and manufacturing land use to residential housing. This can bring new residents to areas which contain the legacy of historic Pb contamination. The objective of this study was to evaluate the difference in soil Pb concentrations between community parks and greenspaces in areas undergoing rapid redevelopment and land use changes and stable areas without redevelopment. Three high- and three low-risk Pb contaminated areas within NYC were identified based on an additive index that included population growth, industrial land use, and new construction. Soil samples (n=358) were collected across 34 parks and analyzed with an XRF with a subset also analyzed by ICP-MS. Areas within NYC, evaluated in this study, with a high-risk index had significantly (p<0.0001) larger mean concentrations of Pb in soil (374 mg/kg vs. 150 mg/kg, respectively) and double the rate of children under the age of six years with BLL > 5ug/dL (37.94 vs. 18.72 per 1000, respectively) compared to low-risk areas. There was a statistically significant (p <0.05) positive correlation between street density, manufacturing/industrial land density and population density change within 0.40 km of a park and soil Pb concentrations. However, we were unable to estimate the source-specific contribution of Pb concentrations in soil, since many of the variables assessed were correlated with one another. Regardless of the source, large population increases are occurring in areas with elevated soil Pb levels. In the three high-risk areas investigated in this study, the population has increased by over 35,000 residents between 2010 to 2017 compared to just 8,500 in the low-risk areas.

Does sulfuric acid have a ‘protective’ effect on battery recyclers exposed to lead?

ABSTRACT Culturally significant interventions to prevent lead exposure of battery recyclers are required. Sulfuric acid used in batteries causes skin lesions and could facilitate the recognition of hazards. This study explored whether joint exposure to lead and sulfuric acid can be used in interventions to manage hazardous work conditions. Data were collected from 120 informal workers, and the blood lead level was measured. Predictors of blood lead levels were explored using a tobit model. The median blood lead level was 9.45 µg/dL (Q75-Q25: 48.9 µg/dL); when lead and sulfuric acid exposure occurred, the level increased to 11.44 µg/dL, and when exposure to lead and other substances occurred, the level was 11.50 µg/dL. Workers are unaware of the risks of obvious and acute silent chronic exposure. Future preventive interventions could confront the economic benefits of battery recycling with the recognition of susceptibility and severity related to lead and sulfuric acid exposure.

Influence of task-based airborne lead exposures on blood lead levels: a case study of informal automobile repair artisans in Nakuru town, Kenya.

Lead poisoning is an emerging worldwide public health concern, especially in the developing countries. Occupational tasks such as spray painting and welding in informal automobile repair enterprises present risks of exposures to lead generally through inhalation and ingestion. The artisans therefore risk high blood lead (BPb) levels, which is critical to chronic adverse health effects of lead. The study aimed at assessing the influence of occupational tasks on personal airborne lead exposures and to evaluate the association between these exposures with blood lead (BPb) levels among the artisans. A cross-sectional study was conducted in ten informal automobile repair workshops. Task-specific personal inhalable air samples and blood samples were collected concurrently for 20 participants performing five distinct occupational tasks. Lead levels were analysed using inductively coupled plasma atomic emission spectroscopy and data analysed by analysis of variance, simple and multiple linear regressions. The results indicated significant differences in airborne lead (PbA) exposure levels in different occupational tasks (p = 0.000). Lead-acid battery repairs recorded mean PbA exposure level of [76.11 ± (10.81 SE) µg/m3] exceeding the WHO 50µg/m3 airborne lead permissible exposure limit. The average (PbA) exposure level was 22.55 ± (5.05 SE) µg/m3, while the mean (BPb) level was 25.08 ± (3.48 SE) µg/dl. A significant positive correlation between task-based airborne lead with blood lead levels was observed (r = 0.68, p = 0.001). In conclusion, the occupational tasks influenced personal airborne lead exposure levels, which in turn was an important predictor of blood lead levels. The study recommends lead exposure assessments, medical screening and intervention measures to minimize the risk and consequences of occupational exposures to lead among the study population.

Prevalence of Blood Lead among Children Living in Battery Recycling Communities in Greater Jakarta, Indonesia.

This study aimed to assess the prevalence of blood lead levels (BLLs) among children 1 to 5 years old who reside near and distant to informally used lead-acid battery (ULAB) recycling locations and examine risk factors for elevated BLLs. A cross-sectional study was conducted in three greater Jakarta neighborhoods where informal ULAB recycling occurs. Venous BLLs among 279 children were analyzed using portable blood lead testing machines. Demographic, child activities, and sources of lead exposure inside and outside homes were assessed. Multivariate analysis was performed to evaluate factors associated with the prevalence of BLLs. Forty-seven percent of children had BLLs ≥ 5 µg/dL and 9% had BLLs ≥ 10 µg/dL. No differences in geometric mean BLLs were observed between children who lived near and distant to ULAB locations. Older child age groups [Prevalence Ratio (PR) 2.14, 95% Confidence Interval (CI) 1.16, 4.18) and low household income (PR 1.58, 95% CI 1.03, 2.40) were associated with BLLs 5–9 µg/dL. Low educational attainment of the child’s father (PR 3.17, 95% CI 1.23, 8.16) and frequent outdoor child activity (PR 4.93, 95% CI 1.09, 22.21) were predictors of BLLs ≥ 10 µg/dL. This study shows the association between lead exposure among children and environmental sources. Public health officials can consider expanded surveillance, health care provider education, and development of strategies to reduce lead exposure.

Drinking water lead and socioeconomic factors as predictors of blood lead levels in New Jersey's children between two time periods

As blood lead levels have decreased over time, the relative contributions of alternative lead sources warrant further examination. Much attention has been paid to the relative contribution of lead in drinking water, particularly after the discovery of contaminated drinking water in Flint, Michigan which has also renewed interest in the persistent socioeconomic and racial disparities in children's exposure to lead. As the environmental sources of lead exposure are shifting in importance over time, we decided to examine how demographic, socioeconomic, and environmental factors may confound or interact with each other, and whether these relationships have changed over time. The study population included all New Jersey resident children aged 6–26 months with at least one blood lead specimen collected between 2000 and 2004 (n = 288,758) or 2010 and 2014 (n = 326,530). Reported 90th percentile water lead data (in parts per billion) was summarized annually for each water system statewide. Children's blood lead levels have decreased over time from a statewide geometric mean of 2.47 µg/dL (95% CI 2.46, 2.48) between 2000 and 2004 to 1.57 µg/dL (95% CI 1.57, 1.57) between 2010 and 2014. Individual-level factors of child's age and season of blood draw and area-based measures of race, older housing, and poverty were predictors of children's blood lead levels. Conclusions regarding area-based measure of Hispanic ethnicity are limited and require further research. The narrow range and low levels of area-based lead concentrations in drinking water limits the ability to detect associations with blood lead levels. Racial disparities in blood lead continue to persist but economic disparities may be narrowing as blood lead concentrations continue to decline.

Drinking water lead, iron and zinc concentrations as predictors of blood lead levels and urinary lead excretion in school children from Montevideo, Uruguay

The global burden of water-based lead (Pb) exposure on children is largely unknown; however, the importance of water sources as a path of Pb exposure is receiving increased attention due to recent prominent exposure events related to corroded plumbing infrastructure in the US. This study investigated the contribution of Pb in household drinking and cooking water to Pb levels in blood (PbB) and urine (PbU) within 353 early school-aged children from Montevideo, Uruguay. Additionally, the analysis considered the child's iron status and the water content of iron (WFe) and zinc (WZn) in relation to water Pb and blood/urine Pb concentrations. Lead concentrations for both PbB and PbU were fairly low (M ± SD: 4.2 ± 2.1 μg/dL; Median [5%, 95%]: 1.9 [0.6, 5.1 μg/L, respectively]); however 21% of the sample had a PbB >5 μg/dL but ≤ 10 μg/dL. Overall, there was little evidence of an association between water metal concentrations and children's PbB/PbU. However, when the sample was stratified by children's iron status, WPb was positively related to PbU, but negatively related to PbB in iron-replete children, even after adjusting for WFe and WZn. In iron-deficient children, there was no elevation in PbU with increasing WPb. In this sample of children with low Pb levels, there were no overwhelming relationships between WPb and either PbB or PbU, however, there was some evidence that iron-replete status promotes excretion of WPb.

Body Fat Percentage and Hemoglobin Levels Are Related to Blood Lead, Cadmium, and Mercury Concentrations in a Korean Adult Population (KNHANES 2008–2010)

Body stores of lead, cadmium, and mercury are determined by the levels in the circulation, and their levels in blood may be related to hemoglobin levels and their absorption by soft tissue and bone. We investigated the association of body fat percentage, hemoglobin levels, and nutrient intakes with the blood concentrations of lead, cadmium, and mercury in a Korean adult population. This study was based on data from the 2008-2010 Korean National Health and Nutritional Examination Survey (n = 4,522, aged ≥ 20 years), which examined nutritional, biochemical, and health-related parameters. A multiple regression analysis after controlling for covariates of age, body mass index, residence area, education level, smoking and drinking status, and bone mineral density for men, with menopausal status added for women in addition to covariates for men indicated that blood lead and mercury levels were negatively associated with body fat percentage only in men, and blood lead, cadmium, and mercury levels were positively related to hemoglobin levels in both genders. Additionally, blood lead levels were negatively associated with fat and carbohydrate intake in both men and women but blood mercury levels were only in men, but not women. Sodium intake was a positive predictor of blood lead levels in both genders but was a positive predictor of blood cadmium levels only in men. In conclusion, body fat percentage and hemoglobin levels need to be recognized as confounding factors when considering blood levels of lead, cadmium and mercury as biomarkers for their exposure. Fat, carbohydrates and sodium intakes are also associated with heavy metal levels in the circulation.

Association between bone mineral density and blood lead level in menopausal women: Analysis of 2008–2009 Korean national health and nutrition examination survey data

IntroductionWe present data from the Korean National Health and Nutrition Examination Survey 2008–2009 on the association of blood lead levels with bone mineral density (BMD) in menopausal women. MethodsThis cross-sectional analysis was restricted to female participants ≥40 years of age who completed the health examination survey, including blood lead measurement and BMD (n=832). Menopausal status was categorized into pre- and postmenopausal. Postmenopausal status was further categorized into natural and surgical menopause. Multivariate linear regression analyses were performed to determine significant predictors of blood lead level among menopause- and BMD-related variables after adjustment for covariates. ResultsPremenopausal women had a geometric mean blood lead level of 2.000μg/dL, compared with 2.274μg/dL and 2.336μg/dL for naturally and surgically menopausal women, respectively. The data suggested that menopausal status and BMD were predictors of blood lead level among women aged ≥40 years. BMD was significantly inversely associated with blood lead level in menopausal women after adjustment for covariates. DiscussionThis study found a significant inverse association between BMD and the blood lead level in menopausal women in a representative sample of Korean women. A few reports have shown an association between BMD and the blood lead level in Asian populations. This study suggests that postmenopausal bone mineral resorption is related to increased blood lead levels in menopausal women.

Sources of Potential Lead Exposure Among Pregnant Women in New Mexico

The objectives of this study were to ascertain the prevalence and potential sources of lead exposure among pregnant women residing in a socially-disadvantaged immigrant community in Albuquerque, New Mexico. Pregnant women (n=140) receiving prenatal care through a community clinic participated in a structured interview and screening to measure their blood lead levels (BLLs). Potential sources of lead exposure were ascertained by the CDC and New Mexico Department of Health questionnaires. Self-reported risk factors were examined as predictors of BLLs using multiple linear regression and partial least squares discriminant analysis. Most patients were Spanish-speaking (88.6%), Latina (95%), foreign-born (87.1%), lacked health insurance (86.4%), and had a high school education or lower (84.3%). While risk factors were prevalent in this population, only three women (2.1%) had BLLs ≥3μg/dL. Results of multivariate analyses demonstrated that pica symptoms in pregnancy, history of elevated BLLs before pregnancy, use of non-commercial pottery, and living in older houses were important predictors of elevated BLLs. Although the prevalence of other risk factors relevant to immigrant communities (i.e., use of traditional/folk remedies and cosmetics, seasonings and food products from Mexico) was high, they were not predictive of elevated BLLs. Clinics providing prenatal care to immigrant Hispanic communities should carefully assess patients' pica symptoms, use of non-commercial pottery, and a history of elevated BLLs. Moreover, additional efforts need to focus on the development of screening questionnaires which better reflect exposures of concern in this population.

Are Lead Risk Questionnaires Adequate Predictors of Blood Lead Levels in Children?

To evaluate the accuracy of the verbal lead risk assessment tool in identifying the presence of measurable blood lead levels (BLL) in children. A retrospective analysis comparing results of a verbal lead risk assessment tool intended to identify elevated BLL in children with actual capillary fingerstick lead screening laboratory data. Three hundred and forty-nine children aged 5 years and younger enrolled in Head Start during the 2008-2009 school year were evaluated. Sixty-nine children had complete data and were included for final analysis. Results of the verbal lead risk assessment and laboratory capillary fingerstick BLL. All 69 children had measurable BLL. The Pass group, 84.3% of the sample, had BLL scores of 2.2±1.5 μg/dl, while the Fail group, 15.7% of the sample, had BLL scores of 1.5±0.65 μg/dl. There was no significant difference in BLL between children that passed the verbal risk assessment and those that failed ( p>.05). The verbal lead risk assessment did not accurately predict measurable BLL in children. Universal BLL screening for children is necessary to identify low levels of lead so that parents and caretakers of children can be notified and assisted in identifying and eliminating sources of lead exposure.

Blood Lead Levels and Risk Factors in Pregnant Women from Durango, Mexico

ABSTRACT In this cross-sectional study the authors determined blood lead levels (BLLs) and some risk factors for lead exposure in pregnant women. Two hundred ninety-nine pregnant women receiving medical attention by the Secretary of Health, State of Durango, Mexico, participated in this study between 2007 and 2008. BLLs were evaluated with graphite furnace atomic absorption spectrometry. The authors used Student t test, 1-way analysis of variance (ANOVA), and linear regression as statistical treatments. BLLs ranged from 0.36 to 23.6 μg/dL (mean = 2.79 μg/dL, standard deviation = 2.14). Multivariate analysis showed that the main predictors of BLLs were working in a place where lead is used, using lead glazed pottery, and eating soil.

Personal Exposure, Behavior, and Work Site Conditions as Determinants of Blood Lead Among Bridge Painters

Bridge painters are exposed to lead during several job tasks performed during the workday, such as sanding, scraping, and blasting. After the Occupational Safety and Health Administration standard was passed in 1993 to control lead exposures among construction workers including bridge painters, this study was conducted among 84 bridge painters in the New England area to determine the significant predictors of blood lead levels. Lead was measured in personal air and hand wipe samples that were collected during the 2-week study period and in blood samples that were collected at the beginning and at the end of the study period. The personal air and hand wipe data as well as personal behaviors (i.e., smoking, washing, wearing a respirator) and work site conditions were analyzed as potential determinants of blood lead levels using linear mixed effects models. Our results show that the mean air lead levels over the 2-week period were the most predictive exposure measure of blood lead levels. Other individual-level significant predictors of blood lead levels included months worked on bridge painting crews, education, and personal hygiene index. Of the site-level variables investigated, having a containment facility on site was a significant predictor of blood lead levels. Our results also indicate that hand wipe lead levels were significantly associated with higher blood lead levels at the end of the study period compared with the beginning of the study period. Similarly, smoking on site and respirator fit testing were significantly associated with higher blood lead levels at the end of the study period. This study shows that several individual-level and site-level factors are associated with blood lead levels among bridge painters, including lead exposure through inhalation and possible hand-to-mouth contact, personal behaviors such as smoking on site, respirator fit testing, and work site conditions such as the use of better containment facilities. Accordingly, reduction in blood lead levels among bridge painters can be achieved by improving these workplace practices.

Factors Contributing to Blood Lead Levels of U.S. Children

While elemental lead has been removed from a variety of products over the past 30 years, it is still a widely distributed metal in the environment and can be found in old electronics, children's toys, and ceramics resulting in the exposure of young children. To determine what factors contribute to blood lead levels in children, and therefore, help determine possible exposure routes, we assessed the effect of housing and general demographic factors and determined which characteristics had the greatest influence on lead levels for children. Blood lead levels (BLLs), demographic data, and housing data from the third National Health and Nutrition Examination Survey (NHANES) (1988–1994) and the three continuous NHANES cycles (1999–2000, 2001–2002, 2003–2004) were used in these analyses. Using SAS software, potential correlations between BLLs and various characteristics were determined using simple linear regression while multivariate regression was utilized to assess the significance of several factors while controlling for known predictors of blood lead levels in children 1–5 years of age. Age of housing, being non-Hispanic black, and age of child had the greatest effect on lead levels in children. Non-Hispanic black children had significantly higher BLLs than non-minority children even after adjusting for age of child and age of housing; however, significant differences in BLLs among the different races were not observed for children living in housing built prior to 1950. More notably, mean ln[BLL] was significantly associated with lead dust levels, which is consistent with the result that children who attend daycare/preschool have significantly lower BLLs than children who do not. These results demonstrate a complex interaction between several demographic, sociodemographic and housing characteristics in predicting BLLs of U.S. children.

Bone and Blood Lead Levels of Middle Aged Koreans not Occupationally Exposed to Lead

Objectives: In order to investigate the level and the association between bone lead and blood lead levels of non-occupationally, lead-exposed Koreans, the authors studied the lead biomarkers of 137 middle aged Koreans (86 males and 51 females) older than whose age were above 40 years. Methods: The tibia lead level was selected as the bone lead indicator of cortical bone, and the blood lead level was also measured. The tibia lead level was measured by K-shell XRF with 30-minute measurement of each subjects. The blood lead level was analyzed by AAS method. Results: The mean (SD) of the tibia lead level of the 137 study subjects was 3.49 (4.99) μg/g, and tended to be higher. The mean (SD) of tibia lead level in male subjects (was 3.90 (4.88) μg/g) and larger than in that of female subjects (2.80 (5.14) μg/g), but without no statistical significance was observed. The mean (SD) of blood lead level of all total subjects was 3.70 (1.35) μg/dl, and tended to be higher. The mean (SD) of blood lead level in male subjects (was 3.93 (1.25) μg/dl) and larger than in that of female subjects (3.30 (1.42) μg/dl), but without no statistical significance was observed. In multiple regression analysis of blood lead levels after adjusting for covariates, age was a significant independent variable. A weak association of age with tibia lead in female subjects was also observed in multiple regression analysis. Conclusion: The mean (SD) of tibia and blood lead levels of middle aged Koreans whose ages were over 40 years old were 3.49 (4.99) μg/g and 3.70 (1.35) μg/dl, respectively. Age and sex were positive predictors of blood lead level in multiple regression analysis after controlling for the covariates. However, in multiple regression analysis whereas age was weakly association with tibia lead level only in female subjects in multiple regression analysis.

The impact of menopause and lifestyle factors on blood and bone lead levels among female former smelter workers: The Bunker Hill Study

The Bunker Hill mine in Idaho operated from 1886 to 1981. In the 60's and 70's it provided approximately 25% of the primary lead in the United States. Women first began working on the production and maintenance lines in 1972. This study examines the impact of menopause and several occupational and lifestyle factors as determinants of blood and bone lead levels among 73 female former smelter workers. Blood lead levels were analyzed using graphite furnace atomic absorption spectroscopy. The (109)Cd K X-ray fluorescence system was used to measure calcaneus and tibia bone lead content. Information was obtained on reproductive history, alcohol and cigarette consumption, education, and hormone replacement therapy (HRT). Postmenopausal women (n = 47) had significantly (P < 0.002) higher blood lead levels (3.48 microg/dl) than did premenopausal women (n = 26) (2.19 microg/dl). The best predictors of blood lead levels were smoking (>10 or < or =10 cigarettes/day), natural menopause, technical or community college education, manager or technical worker, and past or present use of HRT. The best predictors of calcaneus bone lead levels (P < 0.2) were technical workers, such as miner; natural menopause; and smoking >10 cigarettes/day; level of education; 1-2 pregnancies; and age (>60 years). Lead exposure results in higher blood lead levels especially during menopause.

Bone Density-related Predictors of Blood Lead Level among Peri- and Postmenopausal Women in the United States: The Third National Health and Nutrition Examination Survey, 1988-1994

Because of the long half-life of lead stored in bone (years), skeletal lead stores may be a source of endogenous lead exposure during periods of increased bone demineralization, such as menopause. To test the hypothesis that postmenopausal bone resorption increases blood lead levels, the authors examined cross-sectional associations of bone density-related factors with blood lead levels among women aged 40-59 years from the Third National Health and Nutrition Examination Survey (1988-1994). Factors related to bone turnover were significant predictors of blood lead level. Bone mineral density was significantly inversely related to blood lead levels in log-linear multivariate models that adjusted for age, race/ethnicity, smoking, education, household income, alcohol use, and residence (urban/rural). With menopausal status added to the model, naturally and surgically menopausal women had adjusted median blood lead levels that were 25% and 30% higher, respectively, than those of premenopausal women (2.0 microg/dl). Current use of hormone replacement therapy was associated with significantly lower adjusted median blood lead levels (1.8 microg/dl) than past use (2.6 microg/dl) and never use (2.2 microg/dl). Lead stored in bone may significantly increase blood lead levels in perimenopausal women because of postmenopausal bone mineral resorption. Attention to factors that prevent bone loss may lessen or prevent this endogenous lead exposure.

Relationship of blood and bone lead to menopause and bone mineral density among middle-age women in Mexico City.

To describe the relationship of blood lead levels to menopause and bone lead levels, we conducted a cross-sectional study on 232 pre- or perimenopausal (PreM) and postmenopausal (PosM) women who participated in an osteoporosis-screening program in Mexico City during the first quarter of 1995. Information regarding reproductive characteristics and known risk factors for blood lead was obtained using a standard questionnaire by direct interview. The mean age of the population was 54.7 years (SD = 9.8), with a mean blood lead level of 9.2 microg/dL (SD = 4.7/dL) and a range from 2.1 to 32.1 microg/dL. After adjusting for age and bone lead levels, the mean blood lead level was 1.98 microg/dL higher in PosM women than in PreM women (p = 0.024). The increase in mean blood lead levels peaked during the second year of amenorrhea with a level (10.35 microg/dL) that was 3.51 microg/dL higher than that of PreM women. Other important predictors of blood lead levels were use of lead-glazed ceramics, schooling, trabecular bone lead, body mass index, time of living in Mexico City, and use of hormone replacement therapy. Bone density was not associated with blood lead levels. These results support the hypothesis that release of bone lead stores increases during menopause and constitutes an internal source of exposure possibly associated with health effects in women in menopause transition.

Occupational determinants of bone and blood lead levels in middle aged and elderly men from the general community: the Normative Aging Study.

Few studies of the general population have investigated risk factors for elevated levels of lead in bone in relation to occupation. Six hundred and fifty six community-exposed men had their bone and blood lead levels measured (by K-X-ray fluorescence). Based on their occupational histories, participants were categorized into those who worked in white-collar (WC) occupations (59%) or blue-collar (BC) occupations (41%). No subjects had worked in a primary lead industry (e.g., smelting). In multivariate regression models that adjusted for age, race, education, smoking, alcohol ingestion and retirement status, BC subjects had tibia and patella lead concentrations that were 5.5 (95% CI: 3.2-7.8) and 6.5 (95% CI: 3.1-9.8) microg/g higher than WC subjects, respectively. Interaction terms pairing race with occupational status indicated that in non-white BC subjects, tibia and patella lead levels were higher still by 11.3 (95% CI: -2 to 24.5) and 20.5 (95% CI: 1.2-39.8) microg/g, respectively. Blood lead levels were low for these mostly retired men (mean [SD]: 6.1 [3.9] microg/g) and in multivariate regression models, occupational status was not a significant predictor of blood lead levels; however, an interaction between race and occupational status was also suggested, with non-white BC subjects having blood lead levels that were predicted to be higher by 4.5 (95% CI: 0.3-8.7) microg/dl. Bone lead levels are higher in the men who worked in BC occupations even if they have not worked in primary lead-exposed occupations. This effect is markedly stronger in non-white BC workers and suggests an interaction between occupational exposures and race/ethnicity with respect to cumulative exposure to lead. A similar interaction was suggested by models of blood lead levels.

Impact of breastfeeding on the mobilization of lead from bone.

To evaluate the hypothesis that lactation stimulates lead release from bone to blood, the authors analyzed breastfeeding patterns and bone lead concentrations as determinants of blood lead levels among 425 lactating women in Mexico City for 7 months after delivery (1994-1995). The authors measured in vivo patella and tibia lead concentrations at 1 month postpartum using K x-ray fluorescence. Maternal blood samples and questionnaire information were collected at delivery and at 1, 4, and 7 months postpartum. Blood lead was analyzed using graphite furnace atomic absorption spectroscopy. Mean blood lead level at delivery was 8.4 microg/dl (range: 1.8--23.4). Mean cortical and trabecular lead levels were 10.6 microg/g (range: nondetectable to 76.5) and 15.3 microg/g (range: nondetectable to 85.9), respectively, reflecting a population with elevated and diverse past and current lead exposure. The association of bone lead and breastfeeding with blood lead was estimated using generalized estimating equations. Breastfeeding practices and maternal bone lead were important predictors of blood lead level. After adjustment for bone lead and environmental exposure, women who exclusively breastfed their infants had blood lead levels that were increased by 1.4 microg/dl and women who practiced mixed feeding had levels increased by 1.0 microg/dl, in relation to those who had stopped lactation. These results support the hypothesis that lactation is directly related to the amount of lead released from bone.