The concentrations, distribution and sources of cadmium, copper, lead and zinc in the atmosphere of an urban environment.

The four metals Cd, Cu, Pb and Zn have been measured in residential city air in a relatively small urban environment. The atmospheric concentrations are Cd, 0.516, 0.305; Cu, 12.5, 8.22; Pb, 155, 70.2; and Zn 47.4, 22.4 ng m-3 at two different sites. Except for lead the concentrations are low and more typical of rural areas in more industrialised centres. The concentrations were found to be higher in the colder and more stable air conditions existing during the winter season. Also concentrations on the flat were higher than those on a hillside probably reflecting the influence of thermal inversions. Wind direction influences the concentrations, they being greater when the wind flow comes across the industrial areas of the city. Some of the major sources of the elements are coal, soil, tyre wear and automobile emissions.

The use of peat in the historical monitoring of trace metals in the atmosphere.

The concentrations of lead, zinc, copper, manganese, cadmium and calcium have been measured in three peat bogs. The distribution of Pb, Zn, Mn and Ca are dependent on the position and fluctuations of the water table. They all become depleted in the waterlogged, anaerobic zone. Copper and cadmium are uniformly distributed and appear to be immobilised, probably by the formation of metal/organic complexes, and independent of the acid and redox conditions existing in the bogs. The use of the concentration profiles of the metal ions as a means of historical monitoring of trace metal contamination is complex for Pb, Zn, Mn and Ca but may be more straightforward for Cu and Cd.

Seasonal variations in the concentrations of cadmium, copper, lead and zinc in leaves of the horse chesnut (Aesculus hippocastanum L.).

The concentrations of cadmium, copper, lead and zinc have been measured in the leaves of a deciduous tree the horse chestnut (Aesculus hippocastanum L.) over the period of their lifetime (7 months). The average concentrations for the total sample based on ash weight are: (microg g(-1)) cadmium, 0.197; copper, 129; lead, 294; and zinc, 299. The temporal trends in the concentrations of the metals can be related to their dominant source. Copper and zinc concentrations are highest in the new leaves and decrease with time, suggesting the main source of the elements are uptake from the soil. The decrease occurs partly because of dilution by leaf material as it increases over the growing period. In the case of zinc, however, aerial deposits appear to be also a significant source. Lead concentrations, on the other hand, show an increase with time, which can be related to increasing deposits from aerosol lead arising from the combustion of petrol lead. The increase is enough to offset the dilution effect. For cadmium there is no significant trend, but the tendency is a decrease with time. It is not possible, however, to distinguish between soil uptake and aerial deposit as both are small compared with increase in leaf material.

The transport of airborne trace elements copper, lead, cadmium, zinc and manganese from a city into rural areas.

The fluxes of the elements lead, zinc, copper, cadmium and manganese have been measured in the insoluble component of bulk deposition derived from Christchurch, New Zealand. Lead, zinc, copper and cadmium fluxes follow approximately exponential decay curves away from the city whereas manganese deposition showed little spatial variation. A similar composite source originating in the city is indicated for the lead zinc, copper and cadmium and a different major source occurs for manganese. In the city and nearby rural areas soil is not a major source of atmospheric lead, zinc, copper and cadmium, whereas at remote sites atmospheric levels of these elements are mostly soil derived. Seasonal variations in the bulk deposition are large within the city, and at upwind rural sites. The variations are controlled by meteorological conditions, in particular wind speed and the height of the mixing layer. Compared with overseas studies, the proportion of the metals occurring in the soluble fraction of the bulk deposition is low. This may be due to the relatively dry climate of the area.

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.

A longitudinal study of dentine lead levels and intelligence, school performance and behaviour: the measurement of dentine lead.

Shed deciduous teeth were obtained from a sample of 996 New Zealand children who were participants in a longitudinal study. For each child, estimates of dentine lead were obtained from two samples of dentine. The information was used to estimate the magnitude of random errors of measurement in dentine lead values and it was estimated that between 15 and 20% of the variance in dentine lead values was attributable to random errors of measurement. In addition, dentine lead levels were influenced by small systematic errors of measurement arising from the age at which the tooth was collected and the type of tooth analysed. These sampling factors, however, accounted for less that 3% of the variance in dentine lead values. The implications of these findings for the interpretation of correlations between dentine lead levels and other variables are discussed.

A longitudinal study of dentine lead levels, intelligence, school performance and behaviour. Part I. Dentine lead levels and exposure to environmental risk factors.

Dentine lead levels were obtained for a sample of 996 children who were participants in a longitudinal study of child development. Mean dentine lead levels were just over 6 micrograms g-1 and had a log normal distribution. The relationship between dentine lead values and a number of variables (social background, residence in old weatherboard housing, residence on busy roads, pica) describing exposure to sources of lead was analysed. This showed that all factors made small but statistically significant contributions to variations in dentine lead values and that collectively these factors explained 10% of the variance in lead values. The implications of these results are discussed.

A longitudinal study of dentine lead levels, intelligence, school performance and behaviour. Part III. Dentine lead levels and attention/activity.

The relationship between dentine lead levels and maternal/teacher ratings of inattentive/restless behaviour in children was examined for a birth cohort of New Zealand children. There were small but relatively consistent and stable correlations between dentine lead values and behaviour ratings. After correction for errors of measurement in dentine lead values and behaviour ratings it was estimated that the correlation between lead levels and inattentive/restless behaviour was in the region of +0.18. However, after control for various sources of confounding there was only a small, but statistically significant, correlation of +0.08 between lead levels and inattention/restless in children. It is concluded that the weight of the evidence favours the view that there is a very weak causal association between lead levels and attention and activity levels in children.

A longitudinal study of dentine lead levels, intelligence, school performance and behaviour. Part II. Dentine lead and cognitive ability.

The relationship between dentine lead levels and measures of cognitive ability was examined for a birth cohort of New Zealand children studied until the age of 9. There were small, consistent and stable correlations between dentine lead measures and all measures of cognitive ability including intelligence, word recognition and teacher ratings of school performance. After adjustment for the effects of confounding covariates, sample selection factors and possible reverse causal effects, the correlations between intelligence and dentine lead levels became non-significant. However, small but statistically significant correlations persisted between dentine lead values and all measures of school performance after adjustment for sources of confounding. It is concluded that the weight of the evidence from this analysis favours the hypothesis that low level lead exposure may have deleterious effects on levels of achievement in children.

The analysis and levels of lead in human teeth: a review.

Human teeth are a readily accessible biological tissue for which the analysis of lead has been used for the classification of people in terms of their lead exposure and absorption. However, there are three significant problem areas in the interpretation of the analytical results for lead in teeth. First, the lead is not homogeneously distributed throughout the tooth; secondly, the lead levels vary with tooth type, which relates to the age of a tooth. Lastly, there are significant variations in results from different laboratories, which, in part, reflect problems with contamination, pretreatment and analytical methods. Since teeth provide an integrated historical record of a person's lead exposure they have some attractive features as biological indicators, compared with materials such as blood. But considerable care and attention to detail is necessary to obtain reliable data.

Lead in teeth: the influence of the tooth type and the sample within a tooth on lead levels.

Different sections of permanent teeth have been sampled and the lead levels estimated using carbon furnace AAS. Very high levels of lead (500-3400 micrograms g-1) and other trace metals (Cd, Cu, Fe and Zn) occur on the surface of the teeth, falling off rapidly a few micrometers into the teeth. Lead levels in the bulk enamel of incisors vary depending on the position within the tooth, the highest values occur on the lingual side near the gums and the lowest levels on the labial side near the tooth top. The ratio of the concentration of lead in enamel to dentine and to circumpulpal dentine was found to be 1:2:6, and within the dentine the lead levels were highest in the root dentine. The root dentine in the permanent teeth of eight, near complete or representative, sets of teeth was analysed for lead. The ratio ([Pb]tooth/[Pb]total set) decreased in the order: first molars greater than central incisors greater than lateral incisors greater than canines greater than premolars greater than second molars greater than third molars. This order inversely correlates with the age of formation or eruption of the teeth, i.e. the older teeth have the highest levels of lead in the dentine. Dentine appears to be the best material to use to estimate lead, particularly in relation to the integrated lead intake of a person. Dentine lead was determined in a small sample of deciduous teeth obtained from children living in rural areas. The levels were found to be slightly less than for children living in new housing urban areas and significantly less than for children living in older houses of urban areas.

Lead in house dust of Christchurch, New Zealand: sampling, levels and sources.

Lead in house dust was determined in different areas of Christchurch, New Zealand. The mean lead level in newer (post-1950) areas of the city was 460 micrograms g-1, whereas in older (pre-1950) areas it was 830 micrograms g-1. These levels also relate to the type of building material (brick or wood, respectively) and type of paint used (non-lead or lead paint, respectively). For the newer areas of the city, it was estimated that approximately 90% of the lead was derived from petrol additives (via street dust and aerosol), whereas in the older areas, approximately 50% of the lead was estimated to come from petrol lead and 45% from paint lead.

The sorption of copper (II), manganese (II), zinc (II) and arsenic (III) onto human hair, and their desorption.

Human hair has been studied in relation to sorption from aqueous solutions of Cu2+, Mn2+, Zn2+ and AsO3-(3). At an equilibrium concentration of 0.3 micrograms ml-1 the sorptions are relatively low for Mn (1.1 micrograms g-1) and As (0.1 microgram g-1), and higher for Zn (10 micrograms g-1) and Cu (35 micrograms g-1). But only in the case of copper is the sorption significant relative to the indigenous levels of the elements in the hair. The greater sorption of Cu2+ may be correlated with better binding to the hair fibre, probably both electrostatically and to the sulphur in the keratin. There appears to be at least three modes of attachment, or three mechanisms of attachment of Cu2+ to the hair. An inter-element effect was observed, where Cu2+ severely inhibits the sorption of Zn2+ and Mn2+. Also the total sorption of Cu2+ is reduced on zinc or manganese-treated hair. Some comments are made regarding the results and the problems of exogenous contamination of human hair.