Low-level lead exposure and children.

The adverse effects of environmental lead exposure on the mental development of young children are well established. There is no safe level of blood lead below which children are not affected. Recent research expands our understanding of the impact of lead exposure continuing into later childhood, as well as its effects on children's behaviour. However, social and other environmental factors also contribute to variance in measures of developmental and behavioural outcomes. Lead is associated with only modest effects on children's development, but is a potentially modifiable risk factor. As environmental exposure to lead declines for the whole population, continued specific attention is needed for children living in industrial areas.

Renal tract abnormalities detected in Australian preschool children.

OBJECTIVE: To quantify the incidence of abnormalities in urinalysis and blood pressure from preschool children and their predictive value in detecting renal disease within an Australian community. METHODOLOGY: Urine samples, blood pressure and height measurements and parental reports of significant medical problems were collected from a total of 9355 South Australian preschool children. Seven hundred and forty-three children with abnormal results were investigated in a nephrology outpatient clinic. A control group of 357 children with no detectable abnormality were also recalled, examined and, where appropriate, investigated. RESULTS: Nine thousand, three hundred and fifty-five children were tested. Of these, 0.81% were shown to have a clinically significant renal tract abnormality. The findings included children with urinary tract infections, vesico-ureteric reflux, glomerular disease, renal calculi, essential hypertension and a renal neoplasm. While dipstick-based methods were the most specific indicators of renal tract abnormalities, measurement of blood pressure and urinary beta2-microglobulin were also important in detecting abnormalities. Screening for glycosuria did not result in the detection of significant undiagnosed abnormalities. In the control group with no abnormality detected at testing, there was one case each of aortic coarctation, polycystic kidney disease and vesico-ureteric reflux diagnosed. CONCLUSION: Undiagnosed renal tract abnormalities are present in many Australian preschool children. Most are detectable by a thorough history, examination and urinalysis.

Does breastfeeding at six months predict cognitive development?

There is controversy over whether the method of feeding in infancy affects intellectual development. We investigated the relationship between breastfeeding status at 6 months of age and long-term cognitive development in a cohort of 375 children born in Port Pirie, South Australia, between 1979 and 1982. Cognitive assessments were conducted at ages 2, 4, 7 and 11 to 13 years. After adjustment for sociodemographic, environmental and biomedical factors, a small, statistically non-significant, beneficial effect of breastfeeding on cognitive functioning was observed. Compared with the bottle-fed children, the breast-fed children had a 3.4 (95% CI -0.1 to 6.9), 1.3 (-2.3 to 4.9), 1.2 (-2.0 to 4.4) and 0.8 (-1.9 to 3.5) point advantage on the Bayley Mental Developmental Index at age 2 years, the McCarthy General Cognitive Index at age 4 years and the Wechsler Full-Scale IQ at ages 7 and 11 to 13 years, respectively. Our data suggest that any beneficial effect of breastfeeding on cognitive development is quite small in magnitude.

Preschool hearing screening: evaluation of a parental questionnaire.

OBJECTIVE: To evaluate the validity of a parental questionnaire used to screen preschool children for persistent hearing impairment. METHODOLOGY: Six-hundred and eighty-five children aged 4-5 years from a Metropolitan area of Adelaide, Australia, were enrolled. Each parent completed a questionnaire aimed at detecting parental concerns about hearing impairment. Screening audiometry was then performed. Children who failed the initial audiometry screening underwent repeat audiometry screening 6-8 weeks later. The audiometry and questionnaire data were then compared. RESULTS: Of the 657 children who successfully completed initial audiometry, 544 (83%) passed and 113 (17%) failed. Of the 84 children who had follow-up audiometry, 64 (76%) passed. Parental concerns were identified on questionnaire in 50% of all children. Neither individual questions nor the number of concerns were found to relate to audiometry results. Compared with audiometry results, the hearing screening questionnaire had a sensitivity of 56% and specificity of 52%. CONCLUSIONS: The hearing questionnaire used in this study and in several Australian states is an ineffective screening test for detecting persistent hearing loss.

The prevalence of respiratory symptoms in South Australian preschool children. I. Geographic location.

OBJECTIVE: This study was designed to ascertain the prevalence of respiratory symptoms in South Australian preschool children and to investigate the relationship between prevalence rates and geographic location. METHODOLOGY: Data were collected from 14,124 families with a child aged 4 years 3 months to 5 years of age. This sample represents 73% of the State preschool population of that age. At the time of a routine preschool health check, parents completed a questionnaire regarding their child's respiratory health and place of residence (postcode). RESULTS: Results showed that the prevalence rates were as follows: (i) ever having chest wheezing 38.6%; (ii) chest wheezing within the preceding 12 months 25.2%; (iii) ever having asthma 22.5%; (iv) ever having a dry cough at night 33.7%; (v) ever having bronchitis or cough with sputum 55.3%; (vi) ever having hay fever 29.7%; (vii) prone to excessive head colds 32.6%; and (viii) ever having eczema 18.8%. Over 38% of parents claimed that winter was the season for the most frequent or severe attacks of wheezing and 31.7% claimed no seasonal difference. Winter was the season most associated with episodes of bronchitis (50.9%), with no seasonal difference in episodes for 29.8% of children. Prevalence rates differed by geographic location within South Australia and within the Adelaide metropolitan region. CONCLUSION: This population-based survey shows that over 22% of South Australian 4 to 5 year old preschool children have had (or continue to have) asthma. The study also documented the geographic distribution of respiratory symptom prevalence within South Australia.

The prevalence of respiratory symptoms in South Australian preschool children. II. Factors associated with indoor air quality.

OBJECTIVE: This study investigated the relationship between indoor air quality and the prevalence of respiratory symptoms in South Australian preschool children. METHODOLOGY: Data were collected from 14,124 families with a child aged 4 years 3 months to 5 years of age. This sample represents 73% of the targeted State preschool population. At the time of a routine preschool health check, parents completed a questionnaire regarding: their child's respiratory health and place of residence (postcode), parental smoking, type of fuel used for cooking and heating and method used for home cooling. RESULTS: For preschool children residing in the greater Adelaide region, logistic regression analyses found that having a natural gas stove compared to an electric stove was significantly associated with increased prevalence rates for: (i) asthma (odds ratio [OR] 1.24); (ii) wheezing in the preceding 12 months (OR 1.16); excessive colds (OR 1.14); and hay fever (OR 1.13). The use of a liquid petroleum gas stove compared to an electric stove was not associated with any respiratory symptoms. The use of a flueless gas heater compared to other forms of heating was significantly associated with increased prevalence rates for dry cough (OR 1.26), ever having wheezed (OR 1.15) and wheezing in the preceding 12 months (OR 1.18). The use of a wood fire/heater compared to other forms of heating was significantly associated with a reduced prevalence rate for dry cough (OR 0.84) and ever having wheezed (OR 0.82). Parental smoking was significantly associated with increased prevalence rates for bronchitis (OR 1.21) and ever having wheezed (OR 1.24). The form of home cooling used was not associated with prevalence rates, after accounting for geographic location. Socio-economic status (postcode level) was not generally associated with prevalence rates. CONCLUSIONS: These results suggest that respiratory symptom prevalence is related to the fuel used for cooking and heating and parental smoking. Prospective investigation regarding indoor air quality and respiratory symptoms is required.

Exposure to environmental lead and visual-motor integration at age 7 years: the Port Pirie Cohort Study.

Early childhood exposure to environmental lead may result in subtle deficits in neuropsychological development. Most studies, however, have reported global measures of development, and the findings have not been consistent. In this report, we examine the association between blood lead concentration and a specific aspect of neuropsychological development, visual-motor integration. Each child in a cohort of 494 children living in and around the lead smelting town of Port Pirie, South Australia, was followed for its first 7 years of life. Serial blood samples were collected at various ages to estimate the lifetime burden of each individual. At the time of each blood sampling, systematic information was obtained on a wide range of other variables relevant to child development. We evaluated visual-motor integration at age 7 with the Beery Developmental Test of Visual-Motor Integration (mean score: 13.4). There was an inverse relation between blood lead concentration and visual-motor performance. After adjustment for potential confounding factors, both prenatal and postnatal blood lead concentrations exhibited a dose-related inverse association with children's visual-motor performance. For an increase in life-time average blood lead concentration from 10 micrograms per dl (0.48 mumol per liter) to 30 micrograms per dl (1.45 mumol per liter), the estimated deficit in children's visual-motor performance was 1.6 points (95% confidence interval = 0.3-2.9). The results indicate that visual-motor integration may be a more sensitive index than global measures of development, such as intelligence quotient, for the assessment of lead effects on child development.

Tooth lead levels and IQ in school-age children: the Port Pirie Cohort Study.

The relation between lead concentration in deciduous central upper incisor teeth and intellectual functioning was examined in 262 children who were followed from birth to age 7 years in the lead smelter town of Port Pirie, South Australia, and its environs. Intellectual functioning of the children was assessed over the 3-year period from 1986 to 1989 with the revised Wechsler Intelligence Scale for Children (WISC-R) while each child was in his or her eighth year. There was an inverse relation between tooth lead concentration and intellectual development; the intelligence quotient declined by 2.6 points (90% confidence interval (CI) 0.13-4.9) for each natural-log unit increase in tooth lead concentration, expressed in parts per million. Some WISC-R subscales were more strongly associated with lead exposure than others. In particular, tooth lead was significantly negatively associated with scores for the "Block Design" test (partial regression coefficient -1.25 points per unit of natural-log tooth lead; 90% CI -0.61 to -1.89). No statistically significant interaction between a child's sex and tooth lead concentration was found for any of the WISC-R scales. These findings are in agreement with previously published results from this cohort for which serial blood lead concentrations were used to estimate lifetime lead burden.

Factors influencing parental compliance following school entry health screening.

This study investigated the factors influencing parental action on behalf of their child following a school entry health screening failure. It was predicted that compliance with recommendations to seek further assessment would be related to the screening process variables and the number of barriers to compliance parents faced and that these barriers, and hence compliance, would be influenced by the socio-economic status of the family. It was also expected that when schools were differentiated on adversity factors, the type of school attended would be related to compliance. Results from a sample of parents (n = 1231) showed that the parental non-compliance rate to a referral of their child for further assessment following health screening was 26.1%. Non-compliance was related to both screening process knowledge and satisfaction and the type of barriers to compliance parents experienced. Although the type and number of barriers experienced by parents was related to socio-economic status, the results of correlational and discriminant function analyses indicated that the barriers most strongly related to compliance (e.g. partner's views, time pressure, more serious problems to worry about) were not related to socio-economic status nor type of school attended. These findings provide valuable information for child health service providers as well as those involved in policy making and planning in the general area of community health services.

Environmental exposure to lead and children's intelligence at the age of seven years. The Port Pirie Cohort Study.

BACKGROUND: Exposure to lead in early childhood is thought to result in delayed neuropsychological development. As yet there is little longitudinal evidence to establish whether these effects persist into later childhood. METHODS: We measured IQ scores in 494 seven-year-old children from the lead-smelting community of Port Pirie, Australia, in whom developmental deficits associated with elevated blood lead concentrations had already been reported at the ages of two and four years. Exposure to lead was estimated from the lead concentrations in maternal blood samples drawn antenatally and at delivery and from blood samples drawn from the children at birth (umbilical-cord blood), at the ages of 6 and 15 months and 2 years, and annually thereafter. Data relating to known covariates of child development were collected systematically for each child throughout the first seven years of life. RESULTS: We found inverse relations between IQ at the age of seven years and both antenatal and postnatal blood lead concentrations. After adjustment by multiple regression for sex, parents' level of education, maternal age at delivery, parents' smoking status, socioeconomic status, quality of the home environment, maternal IQ, birth weight, birth order, feeding method (breast, bottle, or both), duration of breast-feeding, and whether the child's natural parents were living together, the relation with lead exposure was still evident for postnatal blood samples, particularly within the age range of 15 months to 4 years. For an increase in blood lead concentration from 10 micrograms per deciliter (0.48 mumol per liter) to 30 micrograms per deciliter (1.45 mumol per liter), expressed as the average of the concentrations at 15 months and 2, 3, and 4 years, the estimated reduction in the IQ of the children was in the range of 4.4 points (95 percent confidence interval, 2.2 to 6.6) to 5.3 points (95 percent confidence interval, 2.8 to 7.8). This reduction represents an approximate deficit in IQ of 4 to 5 percent. CONCLUSIONS: Low-level exposure to lead during early childhood is inversely associated with neuropsychological development through the first seven years of life.

Sociodemographic factors modifying the effect of environmental lead on neuropsychological development in early childhood.

A long-term prospective cohort study was conducted to examine the association between prenatal and postnatal exposure to environmental lead and childhood neuropsychological development. The possible interactive effects of blood lead and some covariates on early development were explored in this study. Our data suggest that gender of the child modifies the effect of lead on the neuropsychological development during early childhood. At the ages of 2 and 4 years, girls appear to be more sensitive than boys to the neuropsychological effects of lead. However, there is no significant modification of the effect of lead by some other covariates, such as parental smoking, socioeconomic status, home environment, birth weight, and the kind of infant feeding. Evidence of interactions between environmental lead exposure and other covariates in the causation of neuropsychological deficits in childhood underscores the desirability of considering both main effects and interactions in this area of research. Such effects, if confirmed, may have implications for public health intervention strategies.

Determinants of blood lead concentrations to age 5 years in a birth cohort study of children living in the lead smelting city of Port Pirie and surrounding areas.

Sources of variation and some principal determinants of blood lead concentration (PbB) were investigated in a cohort of children, followed to age 5 y, who were born near a lead smelter in Port Pirie, South Australia. The child's age and place of residence were the two variables most strongly predictive of PbB. A sharp increase in PbB occurred between 6 and 15 mo of age and was followed by a peak concentration that occurred at approximately 2 y of age, after which PbB steadily and consistently declined. Irrespective of age, the PbBs in children who lived in Port Pirie were significantly higher than levels identified in children who resided outside the city. There was no significant difference in PbB between boys and girls. Elevated PbB at each specific age was associated mainly with increased lead concentrations in the topsoil of the local residential area, employment of the father in the lead industry, parental smoking, and behaviors likely to cause ingestion of dirt. Blood samples taken from children at certain ages and during the warmer months contained more lead than samples obtained during the cooler months. The effects of these determinants on PbB during early childhood were basically consistent in both single and multivariable analyses.

Lead in the placenta, membranes, and umbilical cord in relation to pregnancy outcome in a lead-smelter community.

As part of a cohort study of the effects of chronic exposure to lead on pregnancy outcome and child development, lead concentrations in the umbilical cord and placental tissues (body and membranes) from 9 late fetal deaths, 23 preterm births, and 18 births associated with premature rupture of the amniotic membranes were compared with the lead concentrations in the tissues obtained at 22 normal births. Modest elevations in lead concentration were found in the placental body of late fetal deaths (stillbirths) and preterm births as well as in the cord tissue associated with preterm births and premature rupture of membranes. The geometric mean lead concentration in the membranes from late fetal deaths was 2.73 micrograms/g of dry tissue (95% confidence limits 0.69-10.8), which was 3.5 times higher than the mean found in normal births (0.78 micrograms/g, 95% confidence limits 0.61-1.00). The concentration in the membranes of preterm births was also significantly high, being 1.24 micrograms/G (0.91-1.67). Low correlations of membrane and antenatal blood lead concentrations suggest that other factors in addition to exposure to environmental lead may influence the amount of lead accumulated in the placental membranes.

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.

Port Pirie Cohort Study: environmental exposure to lead and children's abilities at the age of four years.

We studied the effect of environmental exposure to lead on children's abilities at the age of four years in a cohort of 537 children born during 1979 to 1982 to women living in a community situated near a lead smelter. Samples for measuring blood lead levels were obtained from the mothers antenatally, at delivery from the mothers and umbilical cords, and at the ages of 6, 15, and 24 months and then annually from the children. Concurrently, the mothers were interviewed about personal, family, medical, and environmental factors. Maternal intelligence, the home environment, and the children's mental development (as evaluated with use of the McCarthy Scales of Children's Abilities) were formally assessed. The mean blood lead concentration varied from 0.44 mumol per liter in midpregnancy to a peak of 1.03 mumol per liter at the age of two years. The blood lead concentration at each age, particularly at two and three years, and the integrated postnatal average concentration were inversely related to development at the age of four. Multivariate analysis incorporating many factors in the children's lives indicated that the subjects with an average postnatal blood lead concentration of 1.50 mumol per liter had a general cognitive score 7.2 points lower (95 percent confidence interval, 0.3 to 13.2; mean score, 107.1) than those with an average concentration of 0.50 mumol per liter. Similar deficits occurred in the perceptual-performance and memory scores. Within the range of exposure studied, no threshold dose for an effect of lead was evident. We conclude that postnatal blood lead concentration is inversely related to cognitive development in children, although one must be circumspect in making causal inferences from studies of this relation, because of the difficulties in defining and controlling confounding effects.

Determinants of blood lead concentrations of pregnant women living in Port Pirie and surrounding areas.

In the context of a wider prospective investigation into the effects of cumulative exposure to lead, in utero and postnatally, on the outcome of pregnancy and growth and development in early childhood, 831 pregnant women who were living in Port Pirie, South Australia, the site of Australia's largest lead smelter, were recruited between May 1979 and May 1982, and the various factors that were likely to influence their blood lead concentration were examined. No significant difference in blood lead level was found among different stages of pregnancy. Higher concentrations of blood lead were measured in women who resided in areas of high soil lead content and in women who had resided in Port Pirie for three or more years. A low socioeconomic status, the use of water from the reticulated water supply rather than rainwater, an age of 21 years or less, a high body mass index, a low dietary intake of calcium, and cigarette smoking were all factors that were associated with a higher blood lead concentration. Lower blood lead concentrations were observed in women who took iron and folic acid to supplement their diet. Multiple regression analysis of average antenatal blood lead levels confirmed most of the univariate associations.

The Port Pirie cohort study. Blood lead concentrations in early childhood.

A cohort of over 600 children who were born between 1979 and 1982 and accounted for the great majority of all births in Port Pirie, South Australia, and its immediate environs, underwent capillary blood sampling at the ages of 6 months, 15 months, 2 years, and annually thereafter. The mean blood lead concentration (Pb-B) initially rose markedly, peaked at 2 years of age, and subsequently declined gradually at 3 and 4 years of age. No differences in Pb-B were observed between girls and boys. Secular trends in Pb-B at the age of 2 years that were observed in blood samples taken over the 1981-1984 period suggest that both the drought of 1982 and changes in community behaviour may have accounted for some of the age-related variation. The Pb-B was associated positively with surface soil lead concentrations, with a two-fold variation in mean Pb-B between residential zones within Port Pirie. Pb-B was higher in summer than in winter months at the ages of 6 and 15 months, but not at older ages. These findings suggest that lead in dust influences strongly blood lead concentrations in early childhood.