Lead contamination of UK dusts and soils and implications for childhood exposure: An overview of the work of the Environmental Geochemistry Research Group,Imperial College,London, England 1981–1992

Over the course of the last decade, research conducted by the Imperial College Environmental Geochemistry Research Group has focused on the nature and effects of lead in UK dusts and soils. An initial nationwide reconnaissance survey demonstrated that approximately 10% of the population is exposed to lead levels in excess of 2,000 g g^–1 in house-hold dust. Subsequent exposure studies revealed that for 2 year old children in the UK urban environment, approximately 50% of lead intake was from dust ingested as a result of hand-to-mouth activity. Follow-up computer controlled scanning electron microscopy (CCSEM) analysis of urban household dust and particulate material wiped from children's hands showed that important sources of dust lead include lead-based paint, road dust and soils. CCSEM identification of specific soil lead tracer particles (from minewaste contaminated soils) in dusts and on children's hands further documented the important role of soil as a source of exposure. Speciation studies of soil lead of this origin indicated that the form of the lead, which is largely influenced by the soil environment, is the primary control on bioavailability. It appears that although lead of minewaste origin may be present at elevated levels in dusts and soils, it does not necessarily contribute to elevated blood lead levels when the lead is present in relatively insoluble form.     

Distribution of lipids between the zooxanthellae and animal compartment in the symbiotic sea anemoneAnemonia viridis: Wax esters,triglycerides and fatty acids

The temperate sea anemoneAnemonia viridis (Forskäl) contained about 11% lipid on a dry weight basis when maintained at light levels of about 10µE m^–2 s^–1 and a temperature of 10°C. Aposymbiotic forms of the anemone had similar lipid levels. These values are very low compared with tropical symbiotic Anthozoa in which lipid levels constitute up to 50% of dry weight. In symbioticA. viridis, <6% of total lipid consisted of the storage lipids, wax esters and triglycerides. Most of the triglyceride was stored in the animal tissues rather than the zooxanthellae. Zooxanthellae contained only small amounts of wax esters. An analysis was made of the wax ester, triglyceride and fatty acid composition of symbiotic anemones, isolated zooxanthellae and aposymbiotic anemones. Wax ester composition was similar in symbiotic and aposymbiotic forms. However, triglyceride composition differed. In particular trimyristin (C42) was found only within the symbiotic association. Fatty acids showed a high degree of unsaturation, and acids with both even and odd numbers of carbon atoms were found. The most abundant fatty acid was 16:0 in all samples, except for the total lipids from zooxanthellae in which the major fatty acid wastrans-18:1.     

Trace elements in the human environment: Problems and risks

Early studies on the possible influences of environmental geochemistry and health were concerned with major diseases such as cancer or multiple sclerosis. They were generally confined to simple comparisons of geochemical and epidemiological maps and corresponding rural areas. Subsequently, studies of dental health produced evidence for the roles of environmental fluoride, selenium, molybdenum and lead in the aetiology of caries. In recent decades lead has been closely studied. Most people in the western world live in urban areas, rather than rural areas, and research on lead has yielded much information on the distribution of the element in streets, parks and gardens of cities and in the home environment. The role of lead in human health has thereby been better understood. Cadmium, selenium and aluminium are good candidates for future study but success will depend on applying appropriate methods of investigation and here the experiences from research on lead are a valuable model to follow.This paper is based on a keynote lecture at the start of the SEGH conference.     

Data handling and pattern recognition for metal contaminated soils

In the laboratory sciences good experimental design minimises the effects of any disturbing variables so that hypotheses are amenable to to relatively unambiguous testing. But in the field sciences such variables cannot be controlled and data are inherently variable. Subsequent hypothesis testing must rely on a careful statistical interpretation of noisy data. This paper describes one systematic approach to interpreting the results from surveys of metal contaminated soils. Since contaminating metals are also present naturally in soil, anthropogenic excesses are recognised through statistical tests on the data. The nature of pollution processes also leads to the generation of distinct spatial patterns which may be evaluated through appropriate computergraphic techniques.     

The Contribution of Drinking Water towards Dental Fluorosis: A case study of Njoro Division, Nakuru District, Kenya

This study was carried out to measure the fluoride levels of water consumed in the Njoro division of Nakuru district, Kenya. The sources of drinking water, methods of water storage and utilisation, as well as the perceptions of the local community towards dental fluorosis and the percentage of children with moderate to severe dental fluorosis were also determined. Rainwater had mean fluoride levels of 0.5 mg L^-1, dams 2.4 mg L^-1, wells 4.1 mg L^-1, springs 5.5 mg L^-1, and boreholes 6.6 mg L^-1. Water stored in plastic and cement containers did not show appreciable reduction in fluoride content with storage time; water stored in metal containers reduced fluoride by up to 8.2%; water stored in clay pots had the highest reduction in fluoride content, ranging between 34.3 and 64.7%;. Forty eight point three percent of children observed in the area had moderate to severe dental fluorosis, even though most people in the area did not know the cause of the problem.There is need to educate the community on the causes of fluorosis, and to lay strategies for addressing the issue, such as encouraging more rainwater harvesting, treating drinking water with alum, or using clay pots for storage of drinking water.     

The effect of polluted and leached snow melt waters on the soil bacterial community-quantitative response

The effect of polluted snow melt waters on the number of soil bacteria was determined using soil cores extracted from an upland catchment in the Cairngorm Mountains, Scotland. Total numbers of viable heterotrophic bacteria and bacterial denitrifiers were determined using plate and MPN counts. Separate soil cores were treated with simulated melt waters representative of either the composition of the first melt fraction from polluted or leached snowpacks. The number of bacteria in the Ah soil horizon (Hodgson, 1974) treated with polluted snow melt (PSM) water decreased significantly by 28-fold, but increased by 11-fold in the BC horizon. Denitrifier numbers decreased by 8-fold in the Ah horizon, but increased by over 2-fold lower down the profile. Overall the bacterial community exposed to simulated leached snow melt (LSM) waters showed little change in the Ah horizon. In the BC horizon (Hodgson, 1974), total viable bacterial numbers decreased by 20-fold, but denitrifiers numbers were unaffected.     

Effects of colliery waste on littoral communities in north-east England

Colliery waste input has a detrimental effect on the species richness and alpha diversity of sandy and rocky shore communities in north-east England. On sandy shores at the shore levels Chart Datum (CD) + 1.2 to 1.5 m (low shore) and CD + 2.7 to 3.0 m (mid-shore), a maximum of two species of macroinvertebrates per shore level was found at sites heavily contaminated by colliery waste input. In contrast, typically about eight species were found at uncontaminated shores. At the shore level CD + 4.2 to 4.5 m (high shore), the species richness and diversity of fauna were not detectably affected by colliery waste input. On rocky shores that were uncontaminated, 12-15 species of macroalgae were found, whereas only five to eight species were found at contaminated shores. The absentees were usually ephemeral, early successional species. Macroalgal biomass, although less at contaminated shores, showed no significant relationship with colliery waste input. However, the alpha diversity of animal communities on rocky shores was, on occasions, significantly increased where colliery waste inputs occurred. The physical properties of colliery waste are likely to be the reason for the effects observed on both sandy and rocky shores, since many of the leachable chemicals in colliery waste are leached during the period that it spends on the sea bed before accumulating in the intertidal zone.     

Evaluation of water quality of the Qaraaoun Reservoir,Lebanon: suitability for multipurpose usage

The increased demand on water resources in Lebanon as a resultof: progressive urbanization, socio-economic growth, agriculturalactivities and development of industries is, according to the national authorities, a major critical factor by the year 2010.Political difficulties in earlier years imply a dearth of pertinent data. The objective of this study was to evaluate water quality of the Qaraaoun Reservoir of the Litani River andassess its feasibility for multi-purpose usage as one of the solutions to the aggravated water problems in Lebanon. Sampleswere collected from 18 sampling sites at several dates duringthe dry season. Parameters analysed were, pH, electrical conductivity, TDS, turbidity, alkalinity, Ca, Mg, TH, Cl^-, SO₄ ^2-, NH₃, NO₃ ^-,PO₄ ^3-, Fe, Al, Na, Zn, Cr, Cu and As. The reported data were in compliancewith WHO guidelines, USEPA regulation and EEC directives. Statistical analysis of the data defined three distinct environmental zones and water quality in the central, main zone satisfied most criteria. It is concluded that the reservoir water is fit for multipurpose uses, namely, drinking, domestic,recreational activities, irrigation, fisheries, livestock and industrial, and should be properly managed accordingly.