Lead from dust and water as exposure sources for children

Variability and sampling of lead (Pb) in drinking water: Assessing potential human exposure depends on the sampling protocol

Lead (Pb) in drinking water has re-emerged as a modern public health threat which can vary widely in space and in time (i.e., between homes, within homes and even at the same tap over time). Spatial and temporal water Pb variability in buildings is the combined result of water chemistry, hydraulics, Pb plumbing materials and water use patterns. This makes it challenging to obtain meaningful water Pb data with which to estimate potential exposure to residents. The objectives of this review paper are to describe the root causes of intrinsic Pb variability in drinking water, which in turn impacts the numerous existing water sampling protocols for Pb. Such knowledge can assist the public health community, the drinking water industry, and other interested groups to interpret/compare existing drinking water Pb data, develop appropriate sampling protocols to answer specific questions relating to Pb in water, and understand potential exposure to Pb-contaminated water. Overall, review of the literature indicated that drinking water sampling for Pb assessment can serve many purposes. Regulatory compliance sampling protocols are useful in assessing community-wide compliance with a water Pb regulatory standard by typically employing practical single samples. More complex multi-sample protocols are useful for comprehensive Pb plumbing source determination (e.g., Pb service line, Pb brass faucet, Pb solder joint) or Pb form identification (i.e., particulate Pb release) in buildings. Exposure assessment sampling can employ cumulative water samples that directly capture an approximate average water Pb concentration over a prolonged period of normal household water use. Exposure assessment may conceivably also employ frequent random single samples, but this approach warrants further investigation. Each protocol has a specific use answering one or more questions relevant to Pb in water. In order to establish statistical correlations to blood Pb measurements or to predict blood Pb levels from existing datasets, the suitability of available drinking water Pb datasets in representing water Pb exposure needs to be understood and the uncertainties need to be characterized.

Changes in blood lead levels associated with use of chloramines in water treatment systems

BACKGROUND

More municipal water treatment plants are using chloramines as a disinfectant in order to reduce carcinogenic by-products. In some instances, this has coincided with an increase in lead levels in drinking water in those systems. Lead in drinking water can be a significant health risk.

OBJECTIVES

We sought to test the potential effect of switching to chloramines for disinfection in water treatment systems on childhood blood lead levels using data from Wayne County, located in the central Coastal Plain of North Carolina.

METHODS

We constructed a unified geographic information system (GIS) that links blood lead screening data with age of housing, drinking water source, and census data for 7,270 records. The data were analyzed using both exploratory methods and more formal multivariate techniques.

RESULTS

The analysis indicates that the change to chloramine disinfection may lead to an increase in blood lead levels, the impact of which is progressively mitigated in newer housing.

CONCLUSIONS

Introducing chloramines to reduce carcinogenic by-products may increase exposure to lead in drinking water. Our research provides guidance on adjustments in the local childhood lead poisoning prevention program that should accompany changes in water treatment. As similar research is conducted in other areas, and the underlying environmental chemistry is clarified, water treatment strategies can be optimized across the multiple objectives that municipalities face in providing high quality drinking water to local residents.

The influence of pH and household plumbing on water lead concentration

The water lead concentrations measured in the homes of children who were part of the Edinburgh Lead study are related to the characteristics of the water supply and the household plumbing. At the time of the study one of the City of Edinburgh's two water supplies was lime treated to reduce plumbosolvency but in the second supply this treatment had not yet become effective. This allows us to estimate the extent to which this type of water treatment reduces water lead concentrations, in houses with lead plumbing, to comply with existing and proposed limits for lead in water. The kitchen cold water was supplied from a lead storage tank in 69 (15%) of the houses. These houses had the highest lead concentrations and water tre.

Isotopic ratios of lead in contemporary environmental material from Scotland

Lead emitted into the environment, primarily from the combustion of leaded petrol and industrial activities, retains the isotopic signature of the ore(s) from which it is derived. Leaded petrol, atmospheric particulates and street dust sampled in central Edinburgh between February 1989 and December 1991 had mean(206)Pb/(207)Pb ratios of 1.082 ± 0.024, 1.092 ± 0.011 and 1.109 ± 0.016 respectively. These isotope ratios were found to be depleted in(206)Pb compared with a mean of 1.160 ± 0.012 for tap water in contact with lead pipes and %typical ratios of 1.17-1.19 for British lead ore deposits and coal. Paint, with an observed wide range of 20 Pb(207) Pb ratios (1.083-1.183), appears to have significantly influenced house dust and some street dust(206)Pb(207) values. Such overlaps and influences may hinder the quantitative apportionment, via isotope data, of source and route in general population surveys of human exposure to lead.

Trace elements in street and house dusts: sources and speciation

The sources and speciation of trace elements in street and house dusts are reviewed. Soil is a major component of both dusts, but a number of elements are enriched in both materials. These include Pb, Zn, Cu, Cd, As, Sb, Cr, Ca, Na, Au, Cl and Br. They arise from a number of contributing and polluting sources. In the case of house dust, some elements, such as Cu, Co, As, Sb, Zn, Cd, Au, Cl, C and Pb, are produced in the house. There are a number of problems associated with the determination of the speciation of trace elements in dusts. These include the low concentrations of many of the elements, and the interpretation of the results from selective sequential extractions. The mobility and potential availability of the trace elements from dust lies in the order Cd greater than Zn, Pb greater than Mn, Cu greater Fe.

Validity and interpretation of blood lead levels: a study of Danish school children

Blood lead concentrations were measured in a group of children from a group of 9- to 10-year-old school children in Aarhus, Denmark. The study group was selected as a high-level and a low-level lead group, as identified by the lead concentration in the circumpulpal dentine in deciduous teeth shed 2-3 years previously. The validity of the blood sampling technique was investigated in adult volunteers, and lead was determined by electrothermal atomic absorption. Capillary blood sampling by a finger-stick method was preferred, as the slight contamination caused by this technique was deemed acceptable. The children with the highest dentine lead levels (n = 70), had blood lead concentrations of 0.08-0.63 mumol/l and a geometric mean of 0.28 mumol/l. The children with lowest dentine levels (n = 76) had blood lead concentrations of 0.08-0.70 mumol/l and a geometric mean of 0.18 mumol/l. The blood lead concentrations were compared with interview data on behaviour, family habits, diet, parents' tobacco smoking and occupation, water lead measurements, and traffic counts. A total of 20% of the variation in blood lead was explained by parents' tobacco smoking, the child's number in the sibship, gender, and consumption of canned food at home.

The correspondence between U.K. 'action levels' for lead in blood and in water

This paper considers whether the Department of the Environment's water lead concentration criterion for lead pipe replacement and action in individual cases, i.e. 50 micrograms/l in any sample, is too high when set against the Department of Health's advisory action limit for blood lead concentration of 25 micrograms/100 ml. The relationships between blood lead and water lead concentrations found in the Glasgow and Ayr duplicate diet studies, together with unpublished data from Glasgow and Liverpool, indicate that over 10% of people exposed to an average water lead concentration of 100 micrograms/l (the earlier action level) would have blood lead concentrations above 25 micrograms/100 ml, as would about 4% of those exposed to 50 micrograms/l (the Maximum Admissible Concentration in an EEC Directive). For adults, average water lead concentrations should not exceed 30 micrograms/l to ensure compliance with the limit for blood lead, i.e. so that not more than 2% exceed 25 micrograms/100 ml. However, for one of the critical groups, bottle-fed infants (whose diet is 90% water), average water lead concentrations should not exceed 10-15 micrograms/l. The WHO's Provisional Tolerable Weekly Intake (PTWI) for children (25 micrograms/kg body weight) also implies that their water lead concentrations should not exceed 10-15 micrograms/l.

Blood-lead levels and children's behaviour--results from the Edinburgh Lead Study

The effect of blood-lead on children's behaviour was investigated in a sub-sample of 501 boys and girls aged 6-9 years from 18 primary schools within a defined area of central Edinburgh. Behaviour ratings of the children were made by teachers and parents using the Rutter behaviour scales. An extensive home interview with a parent was also carried out. Multiple regression analyses showed a significant relationship between log blood-lead and teachers' ratings on the total Rutter score and the aggressive/anti-social and hyperactive sub-scores, but not the neurotic sub-score when 30 possible confounding variables were taken into account. There was a dose-response relationship between blood-lead and behaviour ratings, with no evidence of a threshold.

The variability of lead in dusts within the homes of young children

The variability of household dust lead concentration and loadings over the period of about a year has been examined in 10 homes. The overall uncertainty on a single sample is ± 65% for lead concentration and ± 81% for lead loading. Redecoration involving electric sanding and/or blow lamp preparation of painted surfaces is the major cause of variation in lead levels. The effect is short lived, levels returning to normal within 2 months of redecoration ending. There is evidence of a seasonal trend for dust loading and lead loading but not for lead concentration. The implications of these findings for blood lead - dust lead exposure studies are considered.