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.     

Non-occupational lead exposure and hypertension in northern Italy

BACKGROUND: Previous research has addressed the issue that low-level blood lead concentration could be associated with an increased risk of hypertension. METHODS: This paper examines the cross-sectional association between blood lead and hypertension in 630 adult males not employed in activities characterized by specific exposure to lead and living in two Northern Italian cities (Verona and Brescia). The participants, aged 26-69 years, constituted a random sample of the patients in the practice of a general practitioner (Verona) and of regular blood donors (Brescia). Logistic regression analysis was used to evaluate the effects of selected variables (blood lead, blood cadmium, zinc erythroprotoporphyrin, haemoglobin, whole blood viscosity, age, body mass index, smoking habits and alcohol consumption) on the probability of being hypertensive. RESULTS: The blood lead concentration (range: 4.3-46.9 micrograms/dl; median: 14.8 micrograms/dl) was very similar in the two samples, whereas the prevalence of hypertension was significantly higher in the Verona sample than in the Brescia sample (20.4% versus 8.3%). Hypertensive subjects showed significantly higher blood lead levels than normotensive ones. In a preliminary (univariate) analysis blood lead levels, body mass index (BMI) and age were each significantly related to the prevalence of hypertension. After adjusting for age and/or BMI, statistical significance of the relationship between blood lead and hypertension was lost.CONCLUSIONS. The present study showed that blood lead is weakly related to hypertension in non-occupationally exposed men. The statistical significance of this association disappeared when age and BMI were used to make adjustments.     

Childhood lead poisoning in Asturias

We have determined the blood lead levels of 1,242 children, from newborn to 14 years old, and 79 young mothers in a period of 10 months in Asturias (Spain). All of them were selected at random among those who consulted one of the three main hospitals in Asturias, but none were diagnosed as lead poisoning. We have found a mean blood lead level of 22.11 micrograms/dl; 23.55% had high levels (= 25 micrograms/dl). Sex was not significantly associated with blood lead levels either in the whole sample or in different age groups. Blood lead level increases rapidly from birth (19.3 micrograms/dl) to the age of one year (23.3 gamma/dl), fluctuating around this level until the age of 7. Then it declines with age until adolescence (19.6 micrograms/dl). From October (25.5 micrograms/dl) to July (20.9 micrograms/dl) the decrease in lead blood level was statistically significant. No difference has been found between urban and rural population. The decree of urbanization has not been found significant. The mean blood lead level in the mothers was 20.5 micrograms/dl.     

Occupational lead exposure and hearing loss

Studies of adults, children, and laboratory animals suggest an association between lead exposure and hearing loss. A causal relationship might direct mandated medical surveillance of lead-exposed workers to include audiometric testing. A cross-sectional, computerized dataset was obtained from a private occupational health screening company to examine the relationship between blood lead level and hearing loss. Audiometry and blood lead results were available for 183 workers. A statistically significant correlation was found between blood lead level and an elevated hearing threshold at 400 Hz (P = 0.03); no other frequencies showed such a correlation. This finding suggests either an interaction between nose exposure and lead, interaction of other exposure factors (such as cigarette smoking), or that factors other than biomechanical ones render the organ of Corti more susceptible at 4000 Hz. Further evaluation of these questions should be undertaken. Computerized databases created for worker surveillance may be a source for data useful for examining other causal connections in occupational settings.     

Lead exposure of workers in the ceramics industry and relevant factors

To clarify lead exposure and factors relevant to it, an occupational health survey and air lead-concentration survey were conducted among 425 workers in the ceramics industry in the Seto region in Aichi Prefecture. As for biological monitoring, blood lead level was measured according to sex, job, product, factory size and duration of lead exposure. The following major findings were obtained in the present analysis. Workers making dolomite novelties showed higher blood lead levels than those making porcelain novelties, semi-porcelain novelties and tableware. The difference in blood lead level by job was statistically significant, but not that by factory size. In males, the highest blood lead level was found for spray painting work (28.7 micrograms/dl), followed by glazing work (28.0 micrograms/dl), kiln work (23.3 micrograms/dl) and painting work (22.3 micrograms/dl). In females, the blood lead level for painting work (13.5 micrograms/dl) was lower than those for glazing work (26.1 micrograms/dl) and kiln work (31.4 micrograms/dl). The blood lead level was significantly increased with the number of years of lead exposure in females (painting work). It was coincidentally clarified that the environmental lead concentration varied according to the job in which workers were engaged. As protective measures against lead exposure for workers in the ceramics industry, the development of nonlead paint and glaze and the introduction of more effective dust collectors at the workplace should be established.     

Chronic exposure to environmental lead in Chilean infants

BACKGROUND: In Chile, there are several sources of environmental lead exposure. However, the few studies about lead levels in Chilean infants, do not allow to establish the prevalence of high lead levels in this population. AIM: To measure blood lead levels in nursing infants, living in rural and urban areas, from birth until two years of age. SUBJECTS AND METHODS: Newborns from public maternity hospitals in Santiago and a rural area were selected for the study. An umbilical cord blood sample was obtained at birth and venous blood samples thereafter, every 6 months until the age of 24 months. Lead levels were measured by atomic absorption spectrophotometry. Atmospheric lead was measured simultaneously every week in Santiago and the rural area. RESULTS: Three hundred twelve children from Santiago and 113 from the rural area completed the 24 months follow-up. The mean lead exposure for infants living in Santiago and in the rural area was 1.23 +/- 0.66 and 0.19 +/- 0.15 micrograms/m3 respectively (p < 0.001). Mean blood levels were always higher in infants from Santiago, compared to those from the rural area. At 24 months, 4.5% of children from Santiago and 0.7% of children from the rural area had blood lead levels over 10 micrograms/dl. Significant risk factors for high lead levels were recent painting of the house where the infant lives, eating soil, biting banisters and familiar labor exposure to lead. CONCLUSIONS: Infants living in an urban area and exposed to increased atmospheric lead levels have higher blood lead levels than infants living in a rural area.     

Blood lead levels in preschool children in Rawalpindi

Blood lead levels were determined in preschool children residing in Urban areas of Rawalpindi city. Of 92 (50 males and 42 females) children aged one to 5 years were included in the study. Blood lead levels ranged from 7 micrograms/dl to 34 micrograms/dl (mean 18.8 micrograms/dl). The mean lead levels were slightly higher in males (20.3 micrograms/dl) than in females (17.2 micrograms/dl) and over 90% children had lead levels above the acceptable limit of 10 micrograms/dl. Use of leaded petrol, contaminated surma, leaded paints and pica in children are common in our country and may lead to increased lead levels and appropriate measures should be taken to control this trend.     

Declining blood lead levels and changes in cognitive function during childhood: the Port Pirie Cohort Study

CONTEXT: Many studies have found a significant inverse association between early exposure to environmental lead and cognitive function in childhood. Whether these effects are reversible when exposure is reduced is not clear. OBJECTIVE: To assess the reversibility of the apparent effects of lead on cognitive abilities in early childhood by testing whether declines in blood lead concentrations beyond the age of 2 years are associated with improvements in cognition. SETTING: Urban and rural communities surrounding a large lead smelter in Port Pirie, South Australia. PARTICIPANTS: A total of 375 children followed up from birth to the age of 11 to 13 years. DESIGN: Long-term prospective cohort study. MAIN OUTCOME MEASURES: The Bayley Mental Development Index at age 2 years, the McCarthy General Cognitive Index at age 4 years, and IQs from the Wechsler Intelligence Scale (revised version) at ages 7 and 11 to 13 years. RESULTS: Mean blood lead concentrations in the children decreased from 1.02 pmol/L (21 .2 microg/dL) at age 2 years to 0.38 micromol/L (7.9 microg/dL) at age 1 1 to 13 years, but cognitive scores in children whose blood lead concentration declined most were generally not improved relative to the scores of children whose blood lead levels declined least. Changes in IQ and declines in blood lead levels that occurred between the ages of 7 and 11 to 13 years (r= 0.12, P= .09) suggested slightly better cognition among children whose blood lead levels declined most. CONCLUSION: The cognitive deficits associated with exposure to environmental lead in early childhood appear to be only partially reversed by a subsequent decline in blood lead level.     

Survey of lead exposure around a closed lead smelter

OBJECTIVE: To test the hypothesis that elevated lead in soil is positively correlated with blood lead (BPb) levels in children in an urban population surrounding a closed lead smelter, a US Environmental Protection Agency Superfund clean-up site was surveyed. METHOD: A total of 827 volunteers including 490 children under 6 years of age participated. A questionnaire was administered. Blood lead was determined as was lead content of samples of house dust, soil, paint, and water of the participants' homes. RESULTS: The arithmetic mean venous BPb in 490 children between 6 and 72 months of age was 6.9 micrograms/dL (0.33 mumol/L) range 0.7 to 40.2 micrograms/dL (0.03 to 1.94 mumol/L). The BPb of 78 (16%) children in this group was > or = 10 micrograms/dL (0.48 mumol/L). Based on multiple regression modeling, lead in house dust accounted for 18% of the variance in BPb. Lead in paint together with the condition of the house were the main contributors to the dust lead variance (26%) with soil lead accounting for an additional 6%. Lead in paint alone accounted for 3% of the BPb variance. Lead in paint together with the condition of the house accounted for 12% of BPb variance, and lead in soil accounted for an additional 3%. Factors other than environmental lead such as education of parents, household income, and behavior were associated with BPb levels. CONCLUSIONS: The mean BPb in children was below the present level of concern of the Centers for Disease Control and Prevention. Children with BPb of > or = 10 micrograms/L (0.48 mumol/L) tended to live in poorly maintained older houses. Based on these findings lead in soil and paint in well-maintained homes contributed little to the lead exposure of children.     

Exposure to lead among the population of Barcelona: chronologic trends from 1984 to 1995

BACKGROUND: This study was designed to determine current lead exposure in the Barcelona population and to evaluate the changes occurred during the last 10 years. Blood lead concentration was investigated in a random sample of 694 healthy subjects (age range: 0-65 years). PATIENTS AND METHODS: Adults were random selected from a group of blood donors. Samples of children analysed were selected from subjects with a preoperatory analyses without any disease that could modify blood lead levels. Lead levels were determined by atomic absorption spectrometry. RESULTS: Blood lead concentration was 4.06 +/- 1.4 micrograms/dl in umbilical cord, 8.9 +/- 2.9 micrograms/dl in the paediatric population and 7.8 +/- 4.2 micrograms/dl in the total of adults analyzed. There was statistical differences between the younger subjects and the older population. In 1984 the results found were 18.6 +/- 6.6 micrograms/dl. CONCLUSIONS: The results obtained show that in the last 10 years a reduction on the blood lead levels was occurred. This reduction is parallel with a diminish in the lead petrol concentration in the ambient air.     

Effect of occupational lead exposure on immunoglobulin concentration and cellular immune function in man

The evaluation of immunological conditions of 14 workers occupationally exposed to lead and the comparison of these results with those of a non-exposed control group with similar age and sex were the aims of this study. It was determined the mean values of lead in blood. In exposed workers it was 46.9 micrograms/dl while in the control group it was 10.9 micrograms/dl. Levels of immunoglobulin decreasing while increasing lead concentration in blood were found in those exposed. It was also found a significant decrease in the formation for rosette in relation to the control group.     

Increased lead absorption with anemia and slowed nerve conduction in children near a lead smelter

Studies to evaluate the prevalence, sources, and health consequences of lead absorption were conducted among children living near a primary lead smelter. Lead levels in air, soil, and dust were highest at the smelter and decreased with distance. Ninety-nine percent of one- to nine-year-old children living within 1.6 kilometers had blood lead levels greater than or equal 40 mug/dl, indicating increased absorption, and 22% had levels greater than or equal 80 mug/dl. The prevalence of lead levels greater than or equal 40 mug/dl decreased with distance; at 72 kilometers from the smelter it was 1%. Erythrocyte protoporphyrin levels increased with blood lead levels: 17% of children with lead levels of greater than or equal 80 mug/dl were anemic. There was no overt neurologic toxicity. Significant negative correlation was found in 202 five- to nine-year-old children between blood lead levels and motor nerve conduction velocity (r = 0.38, p less than 0.02).     

Toxoplasma gondii recombinant antigens H4 and H11: use in ELISAs for detection of toxoplasmosis in swine

The prevalence of elevated blood lead (PbB) levels in rural and semi-urban areas of Kwazulu/Natal (KZN) as well as the risk factors for elevation of PbB among children in informal settlements are examined. The study involved over 1200 children in two age groups: 3-5 and 8-10 years old. Average PbB level in Besters, an informal settlement in the Durban metropolitan region, was 10 micrograms/dl with 5% of the children showing PbB level of greater than 25 micrograms/dl. By comparison, average PbB value in Vulamehlo, a rural area located 90-120 km from Durban, was 3.8 micrograms/dl and 2% of the PbB was greater than 10 micrograms/dl. The results show that many children in KZN are at risk of being lead poisoned. Household factors that were significantly associated with PbB levels in children included distance from tarred roads, overcrowding, hygienic habits in the household and the burning of solid wastes for heating or cooking. Lack of significant association with child risk behaviors is attributed to the over-riding influence of high levels of contaminated dusts both indoor and outdoor. With recent introduction of unleaded gasoline in South Africa, a number of unique socio-ecological factors are expected to slow the change in PbB levels of children in some townships.     

delta-Aminolevulinic acid in plasma or whole blood as a sensitive indicator of lead effects, and its relation to the other heme-related parameters

To evaluate the subclinical effect of lead exposure, we determined delta-aminolevulinic acid (ALA) levels in plasma (ALA-P), blood (ALA-B), and urine (ALA-U) and the activity of delta-aminolevulinic acid dehydratase (ALAD) in lead workers. Almost all of the ALA molecules in blood were present in plasma and not in blood cells, irrespective of the blood lead concentration (Pb-B). ALA-P or ALA-B levels increased slowly at Pb-B levels below 40 micrograms/dl (slow phase) and rapidly at levels above 40 micrograms/dl (rapid phase). In both phases, ALA-P and ALA-B were well correlated with Pb-B and ALAD activity. The threshold value (no-effect level) of Pb-B for elevation of the ALA-P or ALA-B level was coincident with that for ALAD inhibition; the value was around 5 micrograms/dl. In the rapid phase, ALA-P increased continuously up to 100 micrograms/dl of Pb-B, while ALAD activity reached a plateau. Receiver operative characteristic (ROC) plot analyses indicated that ALA-P and ALAD activity [ALAD(u)] had a similar diagnostic value at Pb-B levels between 10 and 40 micrograms/dl, although ALAD(%), the remaining ALAD activity as a percentage of the whole activity restored by zinc and dithiothreitol, had the most powerful diagnostic efficiency at these Pb-B levels. By contrast, ALA-U and zinc protoporphyrin were less effective for the diagnosis of lead exposure than ALAD and ALA-P. These findings indicate that ALA-P is the best discriminators of lead exposure form baseline to high levels of exposure.     

The relationship of lead in soil to lead in blood and implications for standard setting

As part of a soil lead regulation process, this review was conducted to determine the association between lead in soil and established human health effects of lead or validated biomarkers of lead exposure. We reviewed only studies where soil exposure could be distinguished from other sources of lead and whose design could reasonably be used to infer a causal relationship between soil lead and either biomarkers or health effects. No such studies of health effects were found. Studies describing a quantitative relationship between soil lead and blood lead did meet our criteria: 22 cross-sectional studies in areas with polluted soil; and three prospective studies of soil lead pollution abatement trials. The cross-sectional studies indicated that, compared to children exposed to soil lead levels of 100 ppm, those exposed to levels of 1000 ppm had mean blood lead concentrations 1.10-1.86 times higher and those exposed to soil lead levels of 2000 ppm had blood lead concentrations 1.13-2.25 times higher. The prospective studies showed effects within the ranges predicted by the cross-sectional studies. Differences in results between studies were surprisingly modest and likely explainable by random sampling error, different explanatory variables included in data analyses and differences in methods of measuring lead in environmental specimens.     

A study of the effects of exposure misclassification due to the time-window design in pharmacoepidemiologic studies

This paper presents a model for predicting blood lead levels in adults who are exposed to elevated environmental levels of lead. The model assumes a baseline blood lead level based on average blood lead levels for adults described in two recent U.S. studies. The baseline blood level in adults arises primarily from exposure to lead in diet. Media-specific ingestion and absorption parameters are assessed for the adult population, and a biokinetic slope factor that relates uptake of lead into the body to blood lead levels is estimated. These parameters are applied to predict blood lead levels for adults exposed to a hypothetical site with elevated lead levels in soil, dust and air. Blood lead levels ranging from approximately 3-57 micrograms/dl are predicted, depending on the exposure scenarios and assumptions.     

Assessment of lead exposure of children from K-XRF measurements of shed teeth

Lead is accumulated and immobilized for long periods of time in teeth. Thus the Pb concentration of a tooth can be used as an indicator of the cumulative Pb intake of a child. Shed and extracted teeth were collected from children in Beijing, China and some industrial regions in the Middle Urals in Russia. The Pb levels in the teeth were measured in Philadelphia, PA using an X-ray fluorescence (XRF) technique. Since Pb deposits in the tooth during the entire period that it is in the child, the measured tooth Pb level was divided by the age of the child when the tooth was shed and expressed in terms of (microgram/g-yr). 10% (n = 100) of the teeth from Beijing, China had Pb levels exceeding 5.5 and 3% above 9 micrograms/g-yr. For comparison, in the 1970s when urban environmental Pb levels were elevated, the tooth Pb levels in Philadelphia children were similar, i.e. 10% (n = 298) of the teeth had Pb levels exceeding 7.5 and 6% were above 9 micrograms/g-yr. Children in a more rural setting, Bennington, VT, had no detectable tooth Pb (n = 200). The Pb levels in the teeth from the Urals were much higher; 50% (n = 134) of the teeth had Pb levels exceeding 7.5 and 10% exceeding 17.8 micrograms/g-yr. The tooth Pb levels observed in the teeth from Beijing, and more so from the Urals, indicate that these children are residing in Pb polluted environments. Further studies are required to determine the extent of the Pb pollution and to explore the possibility that there are associated Pb-related health deficits.     

Results of blood lead screening in children referred for behavioral disorders

This study reviews findings from blood lead level screening in children referred to an Attention Deficit Hyperactivity Disorder clinic. Results obtained from 102 children revealed a sample mean blood lead level of 2.29 micrograms/dL and one patient with a mildly elevated blood lead level. Comparing these findings to results of national studies suggests that these children are not at higher risk for elevated lead levels than is the average child living in a similar setting.     

Relationship between lead mining and blood lead levels in children

The authors studied blood lead levels of 226 randomly selected children, aged 6-92 mo, who lived in either a lead-mining area or a nonmining area, and 69 controls. The authors sought to determine to what extent mining activities contributed to blood lead levels in the children. The mean blood lead levels in the study and control groups were 6.52 microg/dl and 3.43 microg/dl, respectively. The corresponding proportions of children with elevated blood lead levels were 17% and 3%. Soil and dust lead levels were up to 10 times higher in the study than the control group. Elevated blood lead levels appeared to result from exposure to both lead-mining waste and lead-based paint. Mining waste was the cause of the higher prevalence of elevated blood lead levels in these children.     

Lead absorption and renal dysfunction in a South African battery factory

OBJECTIVES: To test the association between inorganic lead (Pb) exposure, blood pressure, and renal function in South African battery factory workers, with both conventional and newer measures of renal function and integrity. METHODS: Renal function measures included serum creatinine, urea, and urate (n = 382). Urinary markers (n = 199) included urinary N-acetyl-beta-D-glucosaminidase (NAG), retinol binding protein, intestinal alkaline phosphatase, tissue non-specific alkaline phosphatase, Tamm-Horsfall glycoprotein, epidermal growth factor, and microalbuminuria. RESULTS: Mean current blood Pb was 53.5 micrograms/dl (range 23 to 110), median zinc protoporphyrin 10.9 micrograms/g haemoglobin (range 1.9 to 104), and mean exposure duration 11.6 years (range 0.5 to 44.5). Mean historical blood Pb, available on 246 workers, was 57.3 micrograms/dl (range 14 to 96.3). After adjustment for age, weight and height, positive exposure response relations were found between current blood Pb, historical blood Pb, zinc protoporphyrin (ZPP), and serum creatinine and urate. Blood pressure was not associated with Pb exposure. Among the urinary markers, only NAG showed a positive association with current and historical blood Pb. CONCLUSION: An exposure-response relation between Pb and renal dysfunction across the range from < 40 to > 70 micrograms/dl blood Pb was found in this workforce, with conventional measures of short and long term Pb exposure and of renal function. This could not be explained by an effect on blood pressure, which was not associated with Pb exposure. The findings probably reflect a higher cumulative renal burden of Pb absorption in this workforce in comparison with those in recent negative studies. The results also confirm the need for strategies to reduce Pb exposure among industrial workers in South Africa.