Lead-induced anemia: dose-response relationships and evidence for a threshold.

We conducted a cross-sectional epidemiologic study to assess the association between blood lead level and hematocrit in 579 one to five year-old children living near a primary lead smelter in 1974. Blood lead levels ranged from 0.53 to 7.91 mumol/L (11 to 164 micrograms/dl). To predict hematocrit as a function of blood lead level and age, we derived non-linear regression models and fit percentile curves. We used logistic regression to predict the probability of hematocrit values less than 35 per cent. We found a strong non-linear, dose-response relationship between blood lead level and hematocrit. This relationship was influenced by age, but (in this age group) not by sex; the effect was strongest in youngest children. In one year-olds, the age group most severely affected, the risk of an hematocrit value below 35 percent was 2 percent above background at blood lead levels between 0.97 and 1.88 mumol/L (20 and 39 micrograms/dl), 18 percent above background at lead levels of 1.93 to 2.85 mumol/L (40 to 59 micrograms/dl), and 40 percent above background at lead levels of 2.9 mumol/L (60 micrograms/dl) and greater; background was defined as a blood lead level below 1.88 mumol/L (20 micrograms/dl). This effect appeared independent of iron deficiency. These findings suggest that blood lead levels close to the currently recommended limit value of 1.21 mumol/L (25 micrograms/dl) are associated with dose-related depression of hematocrit in young children.     

Clinician follow-up of children screened for lead poisoning.

OBJECTIVES: This study assessed clinicians' compliance with Centers for Disease Control and Prevention recommendations for follow-up of children with blood lead (BPb) levels of 0.48 mumol/L (10 micrograms/dL) or higher. METHODS: Clinicians' success at follow-up was determined for 3 BPb ranges: > or = 0.97 mumol/L, 0.73 through 0.92 mumol/L, and 0.48 through 0.68 mumol/L (> or = 20 micrograms/dL, 15-19 micrograms/dL, and 10-14 micrograms/dL, respectively). RESULTS: A total of 410 children with elevated BPb levels were followed over a 12-month period; within 4 months, 71% of those with initial levels of 0.97 mumol/L or greater were retested and 57% and 34% of children with initial BPb levels of 0.73 through 0.92 mumol/L and 0.48 through 0.68 mumol/L, respectively, were retested. CONCLUSIONS: Follow-up of children with elevated BPb levels is inadequate within an urban ambulatory care network.     

Pediatric lead screening in a suburban family practice setting

BACKGROUND. The adverse effects of lead on behavioral and intellectual development have been recognized for many years. During the past 10 years several studies have shown that lead is toxic to children at levels previously thought to be harmless. Black children living in urban neighborhoods have been identified as being at greatest risk. METHODS. To determine whether children seen in a suburban family practice center were being exposed to lead, voluntary screening of 1-year-old patients was performed. RESULTS. Over a 7-month period venous specimens for blood lead level were obtained from 40 children. Seventeen (43%) of the children had levels of 0.0 to 0.2 mumol/L (0 to 4 micrograms/dL). Fifteen (38%) had levels of 0.24 to 0.43 mumol/L (5 to 9 micrograms/dL). Eight (20%) children had levels of 0.48 mumol/L (10 micrograms/dL) or greater. The highest value obtained was 0.82 mumol/L (17 micrograms/dL). Seventy-five percent of the children with significantly elevated lead levels resided in suburban communities. CONCLUSIONS. Children seen in a suburban family practice setting are at risk for lead exposure, and screening should be considered by primary care physicians who practice in nonurban settings.     

Lead absorption in indoor firing range users

To determine if users of indoor firing ranges may be at risk from lead exposure, we studied a law enforcement trainee class during three months of firearms instruction. Blood lead levels were obtained before training and at four-week intervals during training. Air lead levels were measured three times during instruction. Blood lead levels rose from a pre-training mean of 0.31 mumol/L to 2.47 mumol/L. Mean air lead levels were above 2,000 micrograms/m3, more than 40 times the Occupational Safety and Health Administration's standard of 50 micrograms/m3. Cumulative exposure to lead and the change in blood lead were positively correlated. Control measures need to be studied to determine their efficacy in decreasing or eliminating this health risk.     

Elevated blood lead levels in children of construction workers.

OBJECTIVES: This study examined whether children of lead-exposed construction workers had higher blood lead levels than neighborhood control children. METHODS: Twenty-nine construction workers were identified from the New Jersey Adult Blood Lead Epidemiology and Surveillance (ABLES) registry. Eighteen control families were referred by workers. Venous blood samples were collected from 50 children (31 exposed, 19 control subjects) under age 6. RESULTS: Twenty-six percent of workers children had blood lead levels at or over the Centers for Disease Control and Prevention action level of 0.48 mumol/L (10 micrograms/dL), compared with 5% of control children (unadjusted odds ratio = 6.1; 95% confidence interval = 0.9, 147.2). CONCLUSIONS: Children of construction workers may be at risk for excessive lead exposure. Health care providers should assess parental occupation as a possible pathway for lead exposure of young children.     

Past pregnancy outcomes among women living in the vicinity of a lead smelter in Kosovo, Yugoslavia.

This analysis compares the rates of spontaneous abortion among women living in the vicinity of a lead smelter with those of women living in a town where blood lead levels were low. Data derive from the obstetric histories of both groups of women obtained while seeking prenatal care for a later pregnancy. A total of 639 women (304 exposed, 335 unexposed) had at least one previous pregnancy and lived at the same address since their first pregnancy. The geometric mean blood lead concentrations in the sample at the time of the interviews were 0.77 mumol/L in the exposed town and 0.25 mumol/L in the unexposed town. The rates of spontaneous abortions in first pregnancies were similar, with 16.4 percent of women in the exposed town and 14.0 percent in the unexposed town reporting loss. The adjusted odds ratio relating town of residence to spontaneous abortion was 1.1 (95% CI = 0.9, 1.4). This analysis represents the first systematic attempt to seek an association between environmental lead exposure and spontaneous abortion. As such, the failure to find a positive association strongly suggests that at the levels of exposure represented in our sample, such an association does not exist.     

Identification of sources of lead in children in a primary zinc-lead smelter environment

We compared high-precision lead isotopic ratios in deciduous teeth and environmental samples to evaluate sources of lead in 10 children from six houses in a primary zinc-lead smelter community at North Lake Macquarie, New South Wales, Australia. Teeth were sectioned to allow identification of lead exposure in utero and in early childhood. Blood lead levels in the children ranged from 10 to 42 micro g/dL and remained elevated for a number of years. For most children, only a small contribution to tooth lead can be attributed to gasoline and paint sources. In one child with a blood lead concentration of 19.7 microg/dL, paint could account for about 45% of lead in her blood. Comparison of isotopic ratios of tooth lead levels with those from vacuum cleaner dust, dust-fall accumulation, surface wipes, ceiling (attic) dust, and an estimation of the smelter emissions indicates that from approximately 55 to 100% of lead could be derived from the smelter. For a blood sample from another child, > 90% of lead could be derived from the smelter. We found varying amounts of in utero-derived lead in the teeth. Despite the contaminated environment and high blood lead concentrations in the children, the levels of lead in the teeth are surprisingly low compared with those measured in children from other lead mining and smelting communities.     

Blood lead in Swedish police officers

BACKGROUND: Shooting with lead-containing ammunition in firing ranges is a well-known source of lead exposure in adults, and police officers may be at risk of lead intoxication. More stringent national lead regulations stimulated a survey of blood lead (PbB) in Swedish police officers with regular shooting habits. METHODS: Police officers considered as the most active shooters on and/or off duty responded to a questionnaire about health, lifestyle, shooting habits, and potential lead exposure. Blood samples were collected and analyzed for PbB and a multivariate regression analysis was performed. RESULTS: The mean PbB in male officers (n = 75) was 0.24 mumol/L (5.0 micrograms/dL); range 0.05-0.88 mumol/L (1.0-18.2 micrograms/dL), and in female officers (n = 3) it was even lower (0.18 mumol/L; 3.7 micrograms/dL). For both sexes combined, a positive correlation (r = 0.55; P < 0.001) of PbB with the number of bullets annually fired both on and off duty was observed, and this finding remained in a multiple regression analysis including age, smoking habits, and latency from last shooting exercise. DISCUSSION: In conclusion, occupational and recreational lead exposure from firing ranges still seems to be a source of lead exposure in Swedish police officers, but it no longer appears to be a health risk. Lead-free communication and well-ventilated indoor firing ranges may have been decisive for this encouraging finding.     

A prospective study of birthweight and length of gestation in a population surrounding a lead smelter in Kosovo, Yugoslavia

This paper tests the hypothesis that exposure to lead during pregnancy is associated with reduced intrauterine growth and an increase in preterm delivery. The sample comprises women, recruited at mid-pregnancy, residing in Titova Mitrovica, a lead smelter town, or in Pristina, a non-exposed town 25 miles away. Both towns are in the province of Kosovo, Yugoslavia. Mean blood lead concentrations (BPb's) at mid-pregnancy were 0.92 mumol/L (+/- 0.38, N = 401) in the exposed town and 0.27 mumol/L (+/- 0.09, N = 506) in the comparison town. No differences were found between towns for either birthweight or length of gestation. Mean birthweight was 3308 (+/- 566) grams in Titova Mitrovica and 3361 (+/- 525) grams in Pristina. Mean length of gestation was 274 (+/- 18.8) days in Titova Mitrovica and 275 (+/- 15.6) days in Pristina. After adjustment for the effects of potential confounders, no significant relationships were found between maternal BPb measured at mid-pregnancy, at delivery or in the umbilical cord and either birthweight, length of gestation, or preterm delivery (less than 37 weeks). We conclude that exposure to environmental lead does not impair fetal growth or influence length of gestation.     

Lead exposure in battery-factory workers is not associated with anemia

Anemia is a manifestation of lead toxicity. However, there are conflicting reports of its prevalence among lead-exposed workers, and it is uncertain whether they should be monitored by periodic hemoglobin (Hb) examinations. To explore the relationship between Hb and lead exposure, we examined the correlation between Hb, blood lead (PbB), and zinc protoporphyrin (ZPP) levels in 961 blood samples obtained from 94 workers in a lead-acid battery plant in Israel between 1980 and 1993. Blood lead levels exceeded 60 micrograms/dL (2.90 mumol/L) in 105 (14%) of the blood samples. The correlation between PbB and logZPP was 0.594. Hb levels did not correlate with PbB or ZPP. We conclude that (a) periodic Hb determinations are not a useful indicator of lead exposure in Israeli industrial workers; (b) the discrepancies between the reported correlation between PbB and Hb levels remain unexplained and in need of further study; and (c) a finding of anemia in a person with PbB levels of up to 80 micrograms/dL should be considered to be due to lead toxicity only after other causes for anemia have been excluded.     

Follow-up screening of lead-poisoned children near an auto battery recycling plant, Haina, Dominican Republic.

In August 1997 we performed a follow-up survey of 146 lead-poisoned children from a community near a previously active auto battery recycling smelter in Haina near Santo Domingo, Dominican Republic. Our follow-up survey confirmed a severe incidence of elevated blood lead (BPb) and erythrocyte protoporphyrin/zinc protoporphyrin (EP-ZnPP) levels. The mean BPb level was 32 micrograms/dL and the mean EP-ZnPP level was 128 micrograms/dL. The frequency distribution of BPb showed that only 9% of the children had BPb levels below the currently acceptable 10 micrograms/dL threshold level, 23% had between 10 and 19 micrograms/dL, 40% had between 20 and 39 micrograms/dL, 27% had between 40 and 99 micrograms/dL, and the remainder had > 100 micrograms/dL. These findings are significantly greater than the mean BPb and EP-ZnPP levels of 14 and 35 micrograms/dL, respectively, in a comparison group of 63 children in Barsequillo, 4 miles away. BPb frequency distributions for these groups were < 10 micrograms/dL (42%), 10-19 micrograms/dL (32%), and 20-39 micrograms/dL (16%); in the remaining 10%, BPb levels were between 40 and 99 micrograms/dL. Similarly, the corresponding frequency distribution of EP-ZnPP levels in Haina children were proportional to the severity of lead poisoning and significantly higher than those of the Barsequillo comparison group. This study reveals that at least 28% of Haina children require immediate treatment; of these, 5% with lead levels > 70 micrograms/dL are also at risk for severe neurologic sequelae, and urgent action is imperative.     

Soil lead abatement and children's blood lead levels in an urban setting.

OBJECTIVES: The effect of abating soil lead was assessed among Baltimore children. The hypothesis was that a reduction of 1000 parts per million would reduce children's blood lead levels by 0.14 to 0.29 mumol/L (3-6 micrograms/dL). METHODS: In 2 neighborhoods (study and control), 187 children completed the protocol. In the study area, contaminated soil was replaced with clean soil. RESULTS: Soil lead abatement in this study did not lower children's blood lead. CONCLUSIONS: Although it did not show an effect in this study, soil lead abatement may be useful in certain areas.     

The Port Pirie cohort study: maternal blood lead and pregnancy outcome.

During a three-year period, 831 pregnant women in and around Port Pirie, South Australia--a lead smelter community with longstanding lead pollution--were enrolled in a cohort study to examine prospectively the relation between body lead burden and pregnancy outcome. Three-quarters of the enrolled women were residents of the Port Pirie municipality; the other women lived in adjacent towns and countryside. At 14-20 weeks' gestation, the Port Pirie resident women had a mean blood lead concentration of 10.6 micrograms/dl, while the mean in the other (non-Port Pirie) women was 7.6 micrograms/dl. Similar differences were observed in maternal blood samples taken at 30-36 weeks, at delivery, and from the umbilical cord. These blood lead measures, in conjunction with information collected on other risk factors, were then examined in relation to pregnancy outcome. Among 749 pregnancies followed to completion, pre-term delivery was statistically significantly associated, in a dose-response manner, with maternal blood lead concentration at delivery. Mothers of late fetal deaths (stillbirths) had blood lead concentrations at 14-20 weeks' gestation similar to those of all the other women but had lower concentrations at delivery than the other women. Outcomes of pregnancy for which no association with blood lead was detected were spontaneous abortion, low birthweight (for births at term), intrauterine growth retardation, premature rupture of the membranes, and congenital anomalies.     

The association of lead-contaminated house dust and blood lead levels of children living on a former landfill in Puerto Rico

Exposure to lead in children living on a former landfill in Vega Baja-Puerto Rico, a United States Environmental Protection Agency (USEPA) designated Superfund Site, is a major health concern. Direct contact with lead-contaminated soil is considered a major exposure source. However, there is a lack of information regarding the contribution of lead-contaminated house dust to children's blood lead concentrations. This study evaluated the relationship between lead contaminated-house dust and children's blood lead levels. Blood from 42 children, aged 6 years old or less, and dust from 29 houses were analyzed for lead, and face-to-face interviews were performed to gather information on potential risk factors for high blood lead levels. Blood lead levels ranged from 0.97 to 7.79 micrograms/dL. Lead values for floors fluctuated from 0.12 to 98.30 micrograms/ft2, with 17% of houses surpassing the USEPA standard of 40 micrograms/ft2. Multiple regression analysis showed that lead in window sills, toy chewing and soil eating habits were significant predictors of blood lead levels. Further investigations aimed at assessing the long-term effects of constant exposure to environmental lead in these children are warranted.     

Decreasing blood lead in Swedish children, 1978-1988

The geometric mean of the blood lead concentrations in 1,781 samples obtained from children during 1978 to 1988 was 46.9 micrograms/l (0.23 mumol/l) (range: 14-250 micrograms/l [0.07-1.2 mumol/l]). There was a significant (p less than .001) decrease in blood lead concentrations of 7%/y in rural and urban areas. In 134 children who were sampled twice, the decrease over 2-y periods was 14%. The striking decrease in blood lead levels is most likely the result of a reduction of lead additives in motor fuel during this period.     

Lead toxicity in the shipbreaking industry: the Ontario experience

Lead exposure occurs during ship demolition when the ship structure has been previously coated with lead-based paint. An investigation and follow-up of employee lead exposure at the 4 shipbreaking operations in Southern Ontario revealed widespread excessive lead exposure. Air sampling results for lead were above the Ontario standard at all locations. 34 of 113 workers (30%) had at least one blood lead above 3.4 mumol/L*; 50% of workers at one company had results above 2.5 mumol/L. At these blood levels, neurologic, renal and hematologic effects may develop. Institution of control measures (appropriate respirators and hygiene practices, worker education and training, prompt employee notification of blood lead levels) reduced employee lead exposure and lowered blood lead results. Continued vigilance and ongoing employee education and training are required to prevent lead toxicity in shipbreaking. *70 micrograms/100 ml = 3.4 mumol/L.     

Lead-contaminated house dust and urban children's blood lead levels.

OBJECTIVES: This study assessed the relationship between lead-contaminated house dust and urban children's blood lead levels. METHODS: A random-sample survey was used to identify and enroll 205 children, 12 to 31 months of age, who had resided in the same house since at least 6 months of age. Children's blood and household dust, water, soil, and paint were analyzed for lead, and interviews were conducted to ascertain risk factors for elevated blood lead (> or = 10 micrograms/dL). RESULTS: Children's mean blood lead level was 7.7 micrograms/dL. In addition to dust lead loading (micrograms of lead per square foot), independent predictors of children's blood lead were Black race, soil lead levels, ingestion of soil or dirt, lead content and condition of painted surfaces, and water lead levels. For dust lead standards of 5 micrograms/sq ft, 20 micrograms/sq ft, and 40 micrograms/sq ft on noncarpeted floors, the estimated percentages of children having blood lead levels at or above 10 micrograms/dL were 4%, 15%, and 20%, respectively, after adjusting for other significant covariates. CONCLUSIONS: Lead-contaminated house dust is a significant contributor to lead intake among urban children who have low-level elevations in blood lead. A substantial proportion of children may have blood lead levels of at least 10 micrograms/dL at dust lead levels considerably lower than current standards.     

Effects of lead exposure on pregnancy outcome and the fetal brain of squirrel monkeys

Eleven pregnant squirrel monkeys were perorally exposed to lead during the latter two-thirds of pregnancy [mean blood lead 0.54 microgram/ml (2.61 mumol/l), range 0.39-0.82 microgram/ml (1.88-3.96 mumol/l)], at a dosing regime producing no maternal toxic symptoms. Lesions similar to lead encephalopathy and growth retardation of the fetal cerebrum were seen in some of the offspring, as well as neurological and behavioral symptoms at adult age. Cerebral lead levels in offspring (an abortion, stillborns, a sacrificed full-term fetus, and a neonatal death) were between 0.1-0.7 microgram/g. Pre- and perinatal mortality, and prematurity, was increased, and the size of the offspring at birth was reduced. The head circumference tended to be reduced postnatally. Zinc protoporphyrin in blood was determined in four of the pregnant monkeys; the mean values were between 0.58-1.05 micrograms/ml (0.93-1.68 mumol/l). These findings represent the first clearly prenatal brain damages described for experimental peroral lead exposure.     

Impression cytology: a practical index of vitamin A status

Impression cytology was performed on 148 Indonesian preschool children of whom half had mild xerophthalmia and half were age-matched control subjects. Subjects were divided into subgroups that reflected the degree of confidence in their true vitamin A status as determined by serum vitamin A levels, clinical examination, and response to therapy. Impression cytology was considered normal if goblet cells were present and abnormal if they were absent. Thirteen of 14 (93%) children with vitamin A-responsive Bitot's spots and night blindness with base-line serum vitamin A less than 20 micrograms/dL (0.70 mumol/L) (group 1, definite deficiency) had abnormal cytology. In contrast, 17 of 18 (94%) children with normal ocular exam and serum vitamin A greater than 25 micrograms/dL (0.87 mumol/L) (group 7, least likely deficient) had normal cytology. Importantly, 12 of 26 (46%) clinically normal children with serum vitamin A levels less than 20 micrograms/dL (0.70 mumol/L) had abnormal impression cytology.     

Port Pirie Cohort study: childhood blood lead and neuropsychological development at age two years.

The Port Pirie Cohort Study is an ongoing prospective study of the relationship between exposure to environmental lead within a lead smelter community, and neuropsychological development in early childhood. Over 600 children, originally recruited during antenatal life, underwent serial blood lead estimations up to two years of age. Systematic interview information was collected on a range of variables, and formal developmental assessment (Bayley Scales of Infant Development) was carried out at 24 months of age. Blood lead concentrations measured antenatally (maternal), at delivery (maternal and umbilical cord) and postnatally at 6, 15 and 24 months were negatively correlated (p less than 0.05) with mental development at 24 months of age. Geometric mean blood lead concentrations (microgram/dl) were 14.3, 20.8 and 21.2 at 6, 15 and 24 months of age respectively. When multiple covariates, including maternal IQ, were controlled for in multiple regression analysis, a statistically significant (p less than 0.01) inverse association was observed between blood lead concentration (PbB) measured at 6 months of age and mental development at 2 years of age. No such association was evident for psychomotor development. When the quality of the home environment (HOME Score) was added to the multiple regression model, the inverse association between blood lead concentration at 6 months of age and mental development at 2 years persisted, albeit less strongly (p = 0.07). From this analysis, it is estimated that a child with with PbB of 30 micrograms/dl at age 6 months will have a deficit of 3.3 points (approximately 3%) on the Bayley Mental Development Scale relative to a child with PbB of 10 micrograms/dl.