Median Blood Lead Levels Research Articles

Blood Lead Levels: Rhoads and Brown Respond

Rothenberg states that the level of concern for blood lead in children should be lowered from 10 μg/dL, but he provides little cogent rationale for doing so. As basic science support, he cites studies that a) exposed isolated neurons to a 3 μM solution of lead (Ishihara et al. 1995), a concentration that is 5,000 times the plasma levels expected in a child with a blood lead level (BLL) of 5 μg/dL (Manton et al. 2001); b) a study of squirrel monkeys exposed in utero to maternal BLLs in the 20- to 70-μg/dL range (Newland et al. 1996); and c) a study of occupationally exposed workers with a median BLL of 17.1 μg/dL that contains no data on neurologic effects of lead (Murata et al. 2003). Rothenberg’s choice of these citations emphasizes how little basic science work has been done on neuro-developmental effects at the very low levels of lead under discussion. There was a 90% decrease in U.S. childhood BLLs from the late 1970s to the late 1990s (Pirkle et al. 1994). If the regression coefficients relating BLLs 135. To our knowledge, no such effect has been noted in the education literature, nor is it evidenced, for instance, among the increasing proportion of U.S. students admitted to U.S. graduate programs (Basken 2006). What measures can be used to look more formally for this IQ improvement? IQ itself is problematic because the Flynn effect and adjustments in test instruments make secular changes in IQ hard to interpret. The teaching content in science and math has likely shifted over this period. Therefore, in our editorial (Brown and Rhoads 2008) we cited reading scores that measure a key skill that has been identified repeatedly as being affected by lead exposure among other factors. Campbell et al. (2000) reported that reading scores, examined with a suitable time lag in large nationally representative samples of children, were virtually unchanged over the critical period of declining lead levels. Rothenberg is correct that modest gains in math and science were recorded, but these changes could easily have other explanations, and they do nothing to explain the absence of any signal in reading scores. Although there may be other explanations for this absence, the simplest explanation of this paradox is that the published regression coefficients relating BLLs < 10 μg/dL to cognitive measures, all of which come from observational studies, are biased. This possibility is suggested by the steepening of the IQ curve at low lead levels [Centers for Disease Control and Prevention (CDC) 2005b]. Regardless of one’s view of the above evidence, it is important to recognize that virtually all of the progress made in eliminating childhood lead poisoning has been through primary prevention—the control or elimination of lead sources before children are exposed. This approach has lowered the proportion of 1- to 5-year-old children with BLLs > 10 μg/dL from well above 50% 30 years ago to 1.6% in 1999–2002 (CDC 2005a). The percentage is almost certainly lower today. Primary prevention has been proven to work and deserves the continuing attention that we described in our editorial (Brown and Rhoads 2008). Primary prevention can, and should, include increased attention to controlling exposures from lead paint hazards, imported foods, medicines, cosmetics, and toys. Renewed emphasis on screening with a lower BLL of concern would be expensive, intrusive to families, and hard to justify in the absence of proven, practical strategies for reducing lead levels in identified children. Further, it would likely deflect needed resources away from the primary prevention effort. The CDC, in collaboration with federal, state, and local agencies, has outlined and begun to implement a comprehensive, society-wide effort to prevent lead exposure in children while maintaining efforts to identify and treat children with elevated BLLs (CDC 2005b). The CDC has also developed specific recommendations for health care and social service providers, scientists, and public health practitioners who are interested in actively participating in these primary prevention efforts by providing valuable leadership and expertise (Binns et al. 2007; CDC 2005b). By working together with federal, state, and local agencies to foster expansion of primary prevention services, these child advocates can accelerate achieving our mutual goal—lead-safe environments for the nation’s children.

High blood lead levels in recreational indoor-shooters

Recreational shooting in indoor firing ranges is very popular in Germany. Lead-containing ammunition is still in use. Therefore we checked the blood lead levels (BLL) from 129 subjects doing several types of shooting disciplines. In total, BLLs of 129 shooters (nine female) from 11 different shooting ranges with a mean age of 49 years were measured. The blood samples were taken after the volunteers had given written informed consent. Determination of lead was carried out by graphite furnace atomic absorption (GF-AAS) under strict internal and external quality control schemes. While individuals shooting only with airguns (n = 20) showed a median BLL of 33 microg/l (range 18-127 microg/l), those who were also users of .22 lr weapons (n = 15) turned out to have a median of 87 microg/l (range 14-172 microg/l). Shooters of .22 lr and large calibre handguns (9 mm or larger) (n = 51) had median 107 microg/l (range 27-375 microg/l) and those only using large calibre handguns (n = 32) had median 100 microg/l (range 28-326 microg/l). The IPSC-group (n = 11) had the highest median with 192 microg/l (range 32-521 microg/l). Our results show clearly that many shooters have high blood levels; some of them are still exceeding threshold limit values (TLVs) for lead exposed workers. Especially for younger women there is a high potential risk if they become pregnant. So there is a clear need for improving the situation whether by use of lead-free ammunition or by better ventilation systems.

Association of Blood Lead Levels with Onset of Puberty in Russian Boys

BackgroundEpidemiologic studies suggest a temporal trend of earlier onset and longer duration of puberty, raising concerns regarding the potential impact of environmental factors on pubertal development. Lead exposure has been associated with delayed pubertal onset in girls; however, epidemiologic data in boys are limited.MethodsWe used multivariable logistic regression models to explore the cross-sectional association of blood lead levels with growth and pubertal onset based on physician-assessed testicular volume (TV) and pubertal staging in 489 boys 8–9 years of age from Chapaevsk, Russia. We used multivariable linear regression models to assess associations of blood lead levels with somatic growth at the study entry visit.ResultsThe median (25th–75th percentile) blood lead level was 3 μg/dL (2–5 μg/dL). Height, weight, body mass index, birth weight, and gestational age were predictive of the onset of puberty as assessed either by TV (> 3 mL), genitalia stage (G2), or both. Blood lead level was inversely associated with height (p < 0.001) and weight (p = 0.06) after adjustment for birth weight, gestational age, and age at examination. In multivariable adjusted analyses, boys with blood lead levels ≥ 5 μg/dL had 43% reduced odds of having entered G2 compared with those with lower levels (odds ratio = 0.57; 95% confidence interval, 0.34–0.95, p = 0.03).ConclusionsRelatively low environmental blood lead levels were associated with decreased growth and differences in pubertal onset in periadolescent Russian boys. Future analyses of this prospective cohort will address pubertal onset and progression in relation to lead and other environmental chemicals.

Blood Lead Levels and Reported Mood Symptoms Among Russian Boys

ISEE-419 Objective: We assessed the associations between blood lead levels with self-reported mood symptoms in the Russian city, Chapaevsk, where concerns exist regarding contamination by dioxins and metals, including lead. Material and Methods: Our study sample included 489 boys aged 8 to 9 years enrolled 2003 to 2005 in a prospective study evaluating associations between environmental exposures and sexual maturation. The boys’ initial study visit included a physical examination, blood sampling, family medical history, and a nurse-administered mood questionnaire. The 5 mood questions assessed current feelings of unhappiness, self-hatred, loneliness, inferiority, or incompetence with possible responses not true, sometimes, or true (coded 1, 2, and 3, respectively). The blood samples were analyzed for lead by Graphite Furnace Atomic Absorption. The association of each mood question with loge-transformed blood lead levels was assessed using ordinal logistic regression models adjusted for parental education and household income. The association of the summary score (sum over the 5 mood questions, higher scores indicate more symptoms) with loge-transformed blood lead levels was assessed using a general linear regression model, adjusting for parental education and household income. Results: The median (25th, 75th percentile) blood lead levels were 3 μg/dL (2–5 μg/dL). The median (25th, 75th percentile) summary mood score was 7 (6–9), with 16% of the boys having scores ≥10. Blood lead levels were significantly associated with more negative symptoms for 3 (unhappiness, self-hatred, inferiority) of the 5 mood questions. There was also a significant association between blood lead levels and higher summary mood scores, with a 1 unit increase in log blood lead associated with an increase of 1.6 points (95% CI: 1.2–2.2) in the mood score. Conclusions: In this cohort of Russian boys, higher blood lead levels were associated with more mood symptoms. Future follow-up of these boys may elucidate the chronicity of this association.

Association of tibia lead and blood lead with end-stage renal disease: A pilot study of African–Americans

The association between body lead burden and kidney disease remains controversial. Fifty-five African–American end-stage renal disease (ESRD) cases and 53 age- and sex-matched African–American controls without known renal disease were recruited from Tulane University-affiliated dialysis clinics and out-patient clinics, respectively. Blood lead was measured via atomic absorption spectrophotometry and tibia lead (a measure of body lead) was measured via 109Cd-based K shell X-ray fluorescence. Median blood lead levels were significantly higher among ESRD cases (6 μg/dL) compared to their control counterparts (3 μg/dL; P<0.001). Although no participants had overt lead poisoning (blood lead ⩾25 μg/dL), seven cases but no controls had blood lead levels above 10 μg/dL ( P=0.006). The median tibia lead level was 17 micrograms of lead per gram of bone mineral (μg/g) and 13 μg/g among ESRD cases and their control counterparts, respectively ( P=0.134). Four ESRD cases (7%), but no controls, had a tibia lead level above 40 μg/g ( P=0.115) while a similar proportion of cases and controls had tibia lead between 20 and 39 μg/g (33% and 32%, respectively; P=0.726). After adjustment for potential confounders, the odds ratios of ESRD associated with a tibia lead ⩾20 μg/g and each four-fold higher tibia lead (e.g., 5–20 μg/g) were 1.55 (95% CI: 0.55, 4.41) and 1.88 (95% CI: 0.53, 6.68), respectively. These findings support the need for prospective cohort studies of body lead burden and renal disease progression.

Lead exposure in an urban community: Investigation of risk factors and assessment of the impact of lead abatement measures

Introduction A battery recycling plant located in an urbanized area contaminated the environment with lead oxides. The Secretary of Environment of the State of São Paulo demanded an evaluation of lead exposure among the population in the vicinity of the plant. Objectives To assess the lead exposure of children, to propose control measures and evaluate the impact of these measures. Methods Cross-sectional study of all children<13 years old in a radius of 1 km from the plant responsible for the contamination. Blood lead levels (BLL) were determined for each child and questionnaires were applied to their parents. Mean BLL were compared before and after control measures were implemented. Logistic regression identified risk factors of lead exposure. Results Of the 850 investigated children, 311 presented BLL above the action limit established by the World Health Organization. Overall, the median BLL was 7.3 μg/dL and it varied according to age of children (higher among 1–5 years old) and distance of the residence from the plant. Risk factors identified for BLL>10 μg/dL were: to live in unpaved areas, parent working in the plant, distance from the plant, to play on the ground, pica, and to drink locally produced milk. After control measures were implemented (closing the plant, soil removal, dust vacuum-cleaning in the households, etc.), a reduction of 46% in BLL was observed considering the 241 re-evaluated children with levels >10 μg/dL. Conclusions This study showed that combined abatement measures were effective in reducing BLL in children living close to a contaminating source. These results informed the decision-making process regarding management of contaminated areas in Brazil.

Blood and urine levels of Pb, Cd and Hg in the general population of the Czech Republic and proposed reference values

The Human Biological Monitoring (HBM) project was launched in the Czech Republic in 1994 as a part of the nation-wide Environmental Health Monitoring System to assess the exposure of the Czech general population to a broad spectrum of environmental contaminants. Over the years 2001–2003, the concentrations of lead (Pb), cadmium (Cd), and mercury (Hg) were determined in whole blood of 1188 adults (blood donors) and 333 children and in urine of 657 adults and 619 children. In adults, the median blood lead (B-Pb) level was 33 μg/l. Men had higher B-Pb levels than women (medians 37 μg/l vs. 25 μg/l). Significantly higher B-Pb levels were observed in smokers compared to non-smokers (36 μg/l vs. 31 μg/l). In children, no sex-dependent differences were observed (median 31 μg/l). In total, the median blood Cd level (B-Cd) in adults was 0.5 μg/l. Smokers showed a median B-Cd level about 3 times as high as non-smokers (1.3 μg/l vs. 0.40 μg/l). Neither sex- nor age-related differences were observed in B-Cd levels. In 65% of children, B-Cd levels were below the limit of detection (LOD). The overall median urinary cadmium level (U-Cd) in adults was 0.31 μg/g creatinine. Significantly higher U-Cd levels were found in women (median 0.39 μg/g creatinine) compared to men (0.29 μg/g creatinine). No significant differences were found between smokers and non-smokers. In more than 50% of children, the U-Cd level was below the LOD (=0.2 μg/l). The median blood mercury (B-Hg) level in adults was 0.89 μg/l. Significant differences were found between smokers (0.80 μg/l) and non-smokers (0.92 μg/l), and between men and women (0.86 μg/l vs. 0.94 μg/l). The median B-Hg level in children was 0.42 μg/l and no sex-related differences were observed. The median urinary mercury (U-Hg) levels were 0.63 μg/g creatinine in adults and 0.37 μg/g creatinine in children. Significantly higher U-Hg levels were obtained in women and non-smokers compared to men and smokers, respectively. The B-Pb, B-Hg, U-Cd, and U-Hg levels significantly correlated with age. The following reference values were recommended for the period 2001–2003: 80, 65 and 55 μg/l for B-Pb and 3.1, 4.0 and 1.5 μg/l for B-Hg in men, women and children, respectively; 1.1 μg/l and 1.2 μg/g creatinine for B-Cd and U-Cd, respectively, in adult non-smokers; 5.4 and 12.0 μg/g creatinine for U-Hg in men and women, respectively, and 3.7 and 5.5 μg/g creatinine for U-Hg in boys and girls, respectively. The previous reference values for B-Pb and B-Cd needed revision and were reduced.

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.

Prospective Study of Blood and Tibia Lead in Women Undergoing Surgical Menopause

Despite the dramatic decline in environmental lead exposure in the United States during the past couple of decades, concern has been expressed regarding mobilization during menopause of existing lead stored in bone. To investigate whether bone lead concentrations decrease and blood lead levels increase, we conducted a prospective study of 91 women who were scheduled to undergo a bilateral oophorectomy for a benign condition at Mount Sinai Hospital in New York City during October 1994 through April 1999. We excluded women who were younger than 30 years of age or who were postmenopausal at the time of the surgery. We observed a small but significant increase in median blood lead levels between the baseline visit and the 6-month visit (0.4 μg/dL, p < 0.0001), particularly for women who were not on estrogen replacement therapy (0.7 μg/dL, p = 0.008). No significant change was observed in blood lead values between 6 and 18 months postsurgery, nor was there evidence of significant changes in tibia lead concentrations during the follow-up period. These findings do not point to substantial mobilization of lead from cortical bone during menopause.

Elevated blood lead levels associated with the consumption of moonshine among emergency department patients in Atlanta, Georgia

Study objectives In February and March 2000, 4 adult emergency care patients were identified with potentially lethal lead toxicity at Grady Memorial Hospital, an urban Atlanta, GA, hospital. All were moonshine drinkers, prompting concern that lead exposure from moonshine was underrecognized in this setting. Methods We conducted a 2-phased, nested, cross-sectional study throughout a 14-day period in the emergency care center of Grady Memorial Hospital. The prevalence phase consisted of demographic data collection, eligibility screening, and a brief interview pertaining to alcohol and moonshine consumption. During the nested phase, a full interview and blood lead analyses were conducted on all consenting moonshine drinkers and a time-matched comparison group of non–moonshine drinkers. Results In the prevalence phase, of 581 patients interviewed, 8.6% reported consuming moonshine in the past 5 years. Moonshine drinkers were predominantly men between the ages of 40 and 59 years. In the nested phase, the median blood lead levels among moonshine drinkers and nondrinkers were 11.0 μg/dL (0.531 μmol/L) and 2.5 μg/dL (0.121 μmol/L), respectively. Moonshine drinkers were significantly more likely to have blood lead levels of 10 μg/dL (0.483 μmol/L) or greater (odds ratio [OR] 10.94; 95% confidence interval 3.76 to 31.85). Patients who consumed moonshine in the previous week were significantly more likely to have a blood lead level of 10 μg/dL (0.483 μmol/L) or greater than were individuals who reported less recent consumption. Patients who consumed moonshine more than once a month were significantly more likely to have a blood lead level of 10 μg/dL (0.483 μmol/L) or greater than were those reporting less frequent use. Moonshine users were more likely to report heavy alcohol use. Conclusion Moonshine consumption was more prevalent than expected in our patient population and was strongly associated with elevated blood lead levels, particularly among recent moonshine drinkers.

Blood lead levels during pregnancy in women living in Rio de Janeiro, Brazil

The present study was designed to determine variations in blood lead levels during pregnancy and the influence of physiological anemia during this period on these findings. An exploratory study was made of a cohort of 38 pregnant women whose blood was tested for lead level and erythrocyte counts at different stages of pregnancy. The values obtained for lead were adjusted to take account of the erythrocyte count values, in order to control the influence of pregnancy-related physiological anemia on blood lead levels. A statistically significant increase in blood lead levels at a 5% level was observed between the first and third trimester. The median blood lead levels for the first, second and third trimester were 5.1 μg/dl, 5.9 μg/dl, and 8.25 μg/dl, respectively (Kruskal–Wallis=11.9, P<0.002). Statistical significance was also shown for raw data, when blood lead levels were not adjusted to erythrocyte count values. The median blood lead levels observed in this latter situation were 5.55 μg/dl, 5.65 μg/dl and 7.3 μg/dl, respectively (Kruskal–Wallis=8.3, P<0.02). It is concluded that there was a significant increase in blood lead concentration during pregnancy in this group of women.

Lead poisoning among pregnant women in New York City: risk factors and screening practices.

This article presents information on pregnant women with incident blood lead levels (BLLs) of 20 microg per deciliter or greater as reported to the New York City Department of Health between September 1996 and June 1999 (n = 33). Almost half of the women were diagnosed during their third trimester of pregnancy, often at their first prenatal visit. The median BLLs at incidence and at last report among women who were retested were 25 and 15 gamma/dL, respectively, a 40% decline. The median incident BLL among newborns (n = 25) was 12 microg/dL. The BLLs were inversely associated with maternal age and length of time in the United States and directly associated with gestational age and pica behavior. Cases were more than twice as likely to be foreign-born women than all women who gave birth in New York City. Prenatal care facilities employing a policy of universal blood lead testing of all pregnant women at the time of their first visit reported disproportionate numbers of cases, accounting for 77% of cases yet only 11% of all births citywide. The findings suggest that (1) the promulgation of recent rules and guidelines for lead risk assessment and screening among pregnant women appears to have been effective in identifying cases that might not have otherwise come to light; (2) case management and environmental interventions were initiated promptly; (3) cases experienced, on average, significant BLL reductions over time; and (4) there is a need for additional public health interventions for pregnant women in urban, multicultural centers. While the data suggest that universal screening may increase case finding among high-risk, immigrant populations, further studies and surveillance are needed to determine systematically the most effective approach.

Elevated blood lead levels in children are associated with lower erythropoietin concentrations

Eighty-six children (mean age, 34 months) were studied to determine whether elevated blood lead levels in children are associated with lower erythropoietin concentrations. The median erythropoietin concentration was 5.9 mIU/mL (range, 2.3 to 11.5 mIU/mL), and the median blood lead level was 0.87 μmol/L (18 μg/dL; range, 2 to 84 μg/dL). Blood lead concentration was inversely and independently related to erythropoietin concentration. (J Pediatr 1999;134:107-9)

Minimal behavioral effects from moderate postnatal lead treatment in rats.

Developmental lead exposure continues to be a worldwide problem. This study investigated the behavioral effects resulting from developmental lead treatment in rats with corresponding physiological measures of lead exposure. Sprague-Dawley rats were treated with 350 ppm lead acetate from birth to weaning via the dam's drinking water. Behavioral measures assessed in the offspring included residential activity tests, complex maze performance, acoustic startle response, emergence behavior (light/dark preference), prepulse inhibition, and ethological assessments of play, dominance, and burrowing. Pb blood levels averaged 53 microg/dl in the dam at the time of offspring weaning and 46 microg/dl in weanling female offspring. Pb levels averaged 277 ng/g and 32 microg/g in the brain and bone, respectively, of female offspring at weaning. No behavioral assessment indicated any lead-related functional alterations nor were there any statistically significant differences when the lead-treated group was restricted to rats in those litters that were above the median Pb blood lead level at weaning. These results indicate that any lead-related functional alterations at this dose may be subtle and require a sufficient demand on the system for detection.

Immunologic findings among lead-exposed workers.

A comprehensive panel of immune parameters was evaluated among 145 lead-exposed workers with a median blood lead level (BLL) of 39 micrograms/dL (range: 15-55 micrograms/dL) and 84 unexposed workers. After adjusting for covariates, we found no major differences in the percentage of CD3+ cells, CD4+ T cells, CD8+ T cells, B cells, or NK cells between lead-exposed and unexposed workers, although the association between lead exposure and the number of CD4+ T cells was modified by age. We also found no differences between exposed and unexposed workers in serum immunoglobulin levels, salivary IgA, C3 complement levels, or lymphoproliferative responses. However, among exposed workers, the percentage and number of B cells were positively associated with current BLL, serum IgG was negatively associated with cumulative lead exposure, and the percentage and number of CD4+/CD45RA+ cells were positively associated with cumulative lead exposure. We found no evidence of a marked immunotoxic effect of lead at the exposure levels studied, although some subtle differences in immunologic parameters were noted.

Risk factors for high blood lead levels among the general population in Taiwan.

Environmental and occupational lead pollution is a common problem in both developing and industrialized countries. The purpose of this study is to evaluate the risk factors for high blood lead levels among the general population in Taiwan. After multi-stage sampling, we randomly selected 2803 subjects (1471 males and 1332 females) for this study. Univariate and multivariate logistic regression analyses were conducted to evaluate the risk of high blood lead. To control for differences in age and gender, all analyses were with age-adjusted and gender-stratified. Among males, the mean age is 46 years (15 to 85 years), mean and median blood lead levels is 7.3 and 6.3 microg/dl, respectively. Among females, the mean age is 43 years (15 to 84 years), mean and median blood lead level is 5.7 and 4.8 microg/dl, respectively. Among males, the history of herbal drug use, drinking water from well or spring sources, and occupational lead exposure are significantly different between relatively high and normal blood lead level subjects. The history of occupational lead exposure, history of herbal drug use, and well or spring sources of drinking water are the major risk factors for high blood lead with odds ratio of 4.62 (95% CI: 2.82-7.55), 3.09 (95% CI: 1.60-5.97), 2.06 (95% CI: 1.13-3.76), and 2.37 (95% CI: 1.39-4.04), respectively. Among females, these characteristics remain important except the sources of drinking water. The history of herbal drug use and occupational lead exposure become the major risk factors for high blood lead with odds ratio of 2.94 (95% CI: 1.26-6.88) and 7.72 (95% CI: 3.51-16.99), respectively. In multivariate logistic regression analyses, we find that the risk factors for high blood lead in both genders include a history of herbal drug use and occupational lead exposure. Among males, the drinking water sources and factories in the neighboring areas are also significant factors for high blood lead. For the goal of reducing prevalence of high blood lead by the year 2000, the improvement and monitoring of the working environment, the careful attention to herbal drug use and the lead-free drinking water sources should be executed as thoroughly as possible to reduce the probability of lead pollution.

Preventing lead poisoning in children.

Lead poisoning is the most significant and prevalent disease of environmental origin among US children. Despite over 100 years' knowledge of the special hazards of lead exposure for young children, it has taken over a century for effective primary prevention to be adopted. Obstacles to primary prevention have included deliberate campaigns by industry to prevent restrictions upon such uses on lead as plumbing, paints, and gasoline additives; influence of industrial support of biomedical research at major US medical schools: lack of appropriate policy mechanisms to identify and control lead exposures; and opposition to investing resources in lead poisoning prevention. The removal of lead from gasoline, which began in the United States in 1972 and was completed in 1995, has resulted in almost fourfold reductions in median blood lead levels in US children from 1976 to 1991. Increased screening and interventions to identify and abate lead sources, such as lead in housing, also contributed to this major public health success. Nevertheless, lead exposures remain prevalent, although increasingly less generally distributed. Perhaps because of the renewed "ghettoization" of lead, support for lead poisoning prevention has waned. Objections to investing public and private resources in screening and source abatement have challenged the continuing commitment of public health officials to prevention. The demonstrable success and social benefits of preventing lead toxicity are cited in support of continued preventive health policies.

A Randomized Trial of the Effect of Dust Control on Children's Blood Lead Levels

Dust control is recommended as one of the cornerstones of controlling childhood lead exposure; however, the effectiveness of dust control has not been demonstrated for children who have low to mild elevations in blood lead (ie, less than 25 micrograms/dL). The objective of this study was to determine whether dust control, as performed by families, had an effect on children's blood lead levels and dust lead levels in children's homes. Randomized, controlled trial. Community-based trial in Rochester, NY. One hundred four children, 12 to 31 months of age at baseline. Families and children were randomized to one of two groups. Families of children in the intervention group received cleaning supplies, information about cleaning areas that are often contaminated with lead, and a cleaning demonstration. Families in the control group received only a brochure about lead poisoning prevention. Baseline measurements of lead in blood, house dust, soil, water, and paint were taken from both groups. Seven months after enrollment, a second blood lead assay was obtained, and lead levels in household dust were measured. The main outcome measures were change in blood lead levels and dust lead levels by treatment group. The median blood lead level of children enrolled in the study was 6.7 micrograms/dL (range, 1.7 to 30.6 micrograms/dL). There was no significant difference in the change of children's blood lead levels or dust lead levels by treatment group. The median change in blood lead levels among children in the intervention group was -0.05 micrograms/dL compared with -0.60 micrograms/dL among those in the control group. There also was no significant difference in the change of dust lead by group assignment, although there was a trend toward a significant difference in the percentage of change in dust lead levels on noncarpeted floors, which was greater among houses in the intervention group. These data suggest that an intervention that consists only of providing cleaning supplies and a brief description of dust control is not effective at reducing blood lead levels among urban children with low to mild elevations in blood lead levels at a 7-month follow-up.

An in-depth analysis of lead effects in a delayed spatial alternation task: assessment of mnemonic effects, side bias, and proactive interference.

This study examined the effects of chronic postweaning lead (Pb) exposure in Long-Evans rats on a series of spatial alternation tasks. All tasks were administered in automated testing chambers, with a nosepoke as the critical response. While neither Pb-exposed group (median blood lead levels: 19 and 39 micrograms/dl, respectively) was impaired in learning the alternation rule, both groups performed more poorly than controls on the alternation task with variable intertrial delays (0, 10, 20, and 40 s). The deficit was constant across delays, arguing against memory dysfunction. Analyses of the responses on individual trials shed further light on the impaired and spared processes in the Pb-exposed rats. First, these analyses revealed stronger side biases in the higher exposure group. One interpretation is that these animals experienced impatience when the longer delays were included, making it more difficult for them to inhibit a prepotent response to a preferred side. In contrast, these trial-by-trial analyses revealed that several other factors-retention interval, semantic proactive interference, and temporal discriminability-exerted similar effects on performance in the control and lead-exposed animals. The use of logistic regression for these trial-by-trial analyses provided a means of simultaneously assessing the influence of several variables on performance, a significant advantage when there is confounding or interactions between variables.

An Evaluation of Unleaded Petrol as a Harm Reduction Strategy for Petrol Sniffers in an Aboriginal Community

In mid 1989, leaded petrol was replaced by unleaded petrol to reduce lead toxicity in petrol sniffers in Maningrida, a remote Aboriginal community in Northern Australia. RETROSPECTIVE REVIEWS: Hospital admissions between 1987 and 1992 due to petrol sniffing were compared for Maningrida and a community using only leaded petrol. Admissions from Maningrida decreased significantly following introduction of unleaded petrol (chi 2 on 2df = 22.25, p < 0.001). Lead and hydrocarbon exposures were also compared for three groups from Maningrida (27 sniffers using only unleaded petrol; 15 exsniffers and 13 nonsniffers) and 24 individuals admitted to hospital for petrol sniffing related illness from other communities using only leaded petrol. Median blood lead levels for hospitalized sniffers (using only leaded petrol). Maningrida sniffers (using only unleaded petrol), exsniffers and nonsniffers were 5.06, 1.87, 1.24 and 0.17 microM/L respectively. There were significant differences between blood lead level, delta-aminolevulinic acid dehydratase activity, and free erythrocyte protoporphyrin for sniffers of leaded and unleaded petrol, whereas these indices were not significantly different for current sniffers and exsniffers in Maningrida. Hydrocarbons were only detectable in the blood of active sniffers (toluene < or = 0.5 micrograms/mL; benzene < or = 0.17 micrograms/mL blood; n-hexane not detected). The elimination of tetraethyl lead from petrol resulted in a significant decrease in hospitalization of petrol sniffers.