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Biomedical subjects

B L Gulson

Publications and source records attributed to B L Gulson.

34 records · Page 2Linked to original sources
PubMed1997

The efficiency of removal of lead and other elements from domestic drinking waters using a bench-top water filter system.

The efficiency of removal of lead (Pb) and other elements from natural drinking waters using a bench-top water filter system was evaluated in three recently-built houses in Sydney, Australia, and two from rural centres. In addition, one filter system was tested for copper (Cu), Pb and cadmium (Cd) under rigorously-controlled laboratory conditions using Sydney water. For two Sydney houses, the efficiency was evaluated using special filter cartridges concomitant with the ordinary filters. Waters after passing through the filter, was sampled when the filter had been exposed to '0', 50, 100, 150, 200, and 250 l respectively and were analysed for lead isotopes and lead concentrations by high precision isotope dilution mass spectrometry. Samples that passed through the filter after '0', 50, 150 and 250 l collections were analysed for four anions and 39 cations by various methods. Sydney water was fairly uniform in its anion and cation composition, whereas water from the two rural areas contained higher concentrations of Ca, Mg and HCO3. Effects of the filter on the water compositions can be summarised into three groups: (1) elements removed during filtration--Ca, Mg, Sr, Ba, Cu, Pb, Zn and Ni. With 'age' of the filter, the efficiency of removal for Pb was maintained in the two houses with Pb concentrations greater than 10 micrograms/l in the first flush water and was maintained for Cu through all concentrations. Ca, Mg, Sr and Ba were largely removed in the first 50 1 of usage. (2) Elements added during filtration--K, Rb, Ag and P. Except for Ag, which was present throughout the testing period, these elements were added only in the first filtration. (3) Elements unaffected by filtration--Al, Si, Na, Fe, Cl and F. Efficiency of Pb removal from tap water by this system depends generally on the initial Pb content in the water. However, it also seems to depend, to some extent, on Pb speciation and water composition, as found in earlier studies of natural waters. The control in filtering efficiency as a function of Pb speciation and chemical composition becomes more important at low initial Pb concentrations in the water. However, the Pb concentrations at which speciation and water composition appear to play a role in filter efficiency are so low that these factors, though scientifically interesting, have no relevance from a practical point of view, especially the impact on human health. Acidification of six sets of duplicate water samples, one sample immediately after collection and the other acidified after more than 2 weeks, showed negligible changes in Pb or Cu concentrations between duplicates.

Anions↗
PubMed1997

Pregnancy increases mobilization of lead from maternal skeleton.

The question of the extent of lead mobilization from the maternal skeleton during pregnancy and lactation is one of the most outstanding problems of lead toxicity. We have undertaken a longitudinal cohort study in an urban environment of European female immigrants of child-bearing age (18 to 35 years) to Australia whose skeletal lead isotopic composition has been determined to be different from that in their current environment. The cohort was to consist of 100 immigrants anticipated to provide 20 pregnant subjects who would be compared with two groups of control subjects: a matched immigrant nonpregnant control group and second-generation Australian pregnant control subjects. Pregnant subjects also serve as their own controls for a comparison of changes during gestation with those before conception. High-precision lead isotopic compositions and lead concentrations are measured in maternal blood and urine prenatally, monthly during gestation, and postnatally for 6 months; they are also measured in infant blood and urine for 6 months; environmental measures are sampled quarterly for 6-day duplicate diet, house dust and water, and urban air and gasoline. Because of continuing public health concerns about lead exposure, interim findings from this cohort are being reported. To date there have been 13 conceptions in immigrant subjects, with 7 births, in addition to 3 conceptions in the Australian control group, with 2 births. PbBs have been generally low, with a geometric mean of 3.0 microg/dl, and have ranged from 1.9 to 20 microg/dl. Increases in PbB of approximately 20% during pregnancy have been detectable even in subjects with low blood lead levels. The skeletal contribution to blood lead level, based on isotopic measurements, has exhibited a mean increase (and standard deviation) of 31% +/- 19% with a range from 9% to 65%. Earlier studies that used lead concentrations only have suggested that blood lead levels increased only during the second half of pregnancy. This increase in blood lead levels has also been observed in the present study. However, in two subjects the increases in total blood lead were also detected in the first 2 months of pregnancy. Changes in isotopic composition and blood lead during gestation for Australian pregnant controls were negligible. The ratio of cord/maternal blood lead levels varied from 0.54 to 1.05, and the ratio for the isotopic composition was 0.993 to 1.002. Results of this study confirm that lead is mobilized from skeletal stores at an accelerated rate during pregnancy and is transferred to the fetus. These results also show that mobilization from long-term stores (i.e., bone) contributes significantly to blood lead levels during pregnancy. Furthermore, exposure of the fetus to lead during pregnancy has implications for interpretations of neurobehavioral disorders attributed to only postnatal exposure. Even after 800 days of residence in Australia, the contribution of European skeletal lead to blood lead in nonpregnant subjects can be on the order of 50%, but the current PbB may give no indication of the former high skeletal lead burden.

Adolescent↗
PubMed1997

Contamination of houses by workers occupationally exposed in a lead-zinc-copper mine and impact on blood lead concentrations in the families.

OBJECTIVE: To evaluate the pathway of leaded dust from a lead-zinc-copper mine to houses of employees, and the impact on blood lead concentrations (PbB) of children. METHODS: High precision lead isotope and lead concentration data were obtained on venous blood and environmental samples (vacuum cleaner dust, interior dustfall accumulation, water, paint) for eight children of six employees (and the employees) from a lead-zinc-copper mine. These data were compared with results for 11 children from occupationally unexposed control families living in the same city. RESULTS: The median (range) concentrations of lead in vacuum cleaner dust was 470 (21-1300) ppm. In the houses of the mine employees, vacuum cleaner dust contained varying higher proportions of mine lead than did airborne particulate matter measured as dustfall accumulated over a three month period. The median (range) concentrations of lead in soil were 30 (5-407) ppm and these showed no evidence of any mine lead. Lead in blood of the mine employees varied from 7 to 25 micrograms/dl and was generally dominated by mine lead (> 60%). The mean (SD) PbB in the children of the mine employees was 5.7 (1.7) micrograms/dl compared with 4.1 (1.4) micrograms/dl for the control children (P = 0.02). The PbB of all children was always < 10 micrograms/dl, the Australian National Health and Medical Research Council goal for all Australians. Some of the control children had higher PbB than the children of mine employees, probably from exposure to leaded paint as six of the eight houses of the control children were > 50 years old. In five of the eight children of mine employees > 20% of PbB was from the lead mine. However, in the other three cases of children of mine employees, their PbB was from sources other than mine lead (paint, petrol, background sources). CONCLUSIONS: Houses of employees from a lead mine can be contaminated by mine lead even if they are not situated in the same place as the mine. Delineation of the mine to house pathway indicates that lead is probably transported into the houses on the clothes, shoes, hair, skin, and in some cases, motor vehicles of the workers. In one case, dust shaken from clothes of a mine employee contained 3000 ppm lead which was 100% mine lead. The variable contamination of the houses was not expected given the precautions taken by mine employees to minimise transportation of lead into their houses. Although five out of the eight children of mine employees had > 20% mine lead in their blood, in no case did the PbB of a child exceed the Australian National Health and Medical Research Council goal of 10 micrograms/dl. In fact, some children in the control families had higher PbB than children of mine employees. In two cases, this was attributed to a pica habit for paint. The PbB in the children of mine employees and controls was independent of the source of lead. The low PbB in the children of mine employees may reflect the relatively low solubility (bioavailability) of the mine dust in 0.1 M hydrochloric acid (< 40 %), behaviour--for example, limited mouthing activity--or diet.

Adult↗
PubMed1997

Dietary lead intakes for mother/child pairs and relevance to pharmacokinetic models.

Blood and environmental samples, including a quarterly 6-day duplicate diet, for nine mother/child pairs from Eastern Europe have been monitored for 12 to >24 months with high precision stable lead isotope analysis to evaluate the changes that occur when the subjects moved from one environment (Eastern Europe) to another with different stable lead isotopes (Australia). The children were between 6 and 11 years of age and the mothers were between 29 and 37 years of age. These data were compared with an Australian control mother/child pair, aged 31 and 6 years, respectively. A rationale for undertaking this study of mother/child pairs was to evaluate if there were differences in the patterns and clearance rates of lead from blood in children compared with their mothers. Blood lead concentrations ranged from 2.1 to 3.9 microg/dl in the children and between 1.8 and 4.5 microg/dl in the mothers, but the mean of differences between each mother and her child did not differ significantly from zero. Duplicate diets contained from 2.4 to 31.8 microg Pb/kg diet; the mean+/- standard deviation was 5.5 +/- 2.1 microg Pb/kg and total daily dietary intakes ranged from 1.6 to 21.3 microg/day. Mean daily dietary intakes relative to body weight showed that the intake for children was approximately double that for the mothers (0.218 vs. 0. 113 microg Pb/kg body weight/day). The correlations between blood lead concentration and mean daily dietary intake either relative to body weight or total dietary intake did not reach statistical significance (p>0.05). Estimation of the lead coming from skeletal (endogenous) sources relative to the contribution from environmental (exogenous) sources ranges from 8 to 70% for the mothers and 12 to 66% for the children. The difference between mothers and children is not statistically significant (p = 0.28). The children do not appear to achieve the Australian lead isotopic profile at a faster rate than their mothers. These data provide evidence that the absorption or uptake of lead from dietary sources is similar in adult females and children of the age in this study. In spite of lower bone lead and faster bone remodeling and recycling in children compared with adult females, we see no differences between the mothers and their children in overall contribution of tissue lead to blood lead. Results from this study suggest that fractional absorption of ingested lead by children 6-11 years of age is comparable with absorption patterns observed among adult females in the 29-37-year-old age range. Because pharmacokinetic models apply a 40-50% absorption even for 7-year-old children, further investigations on fractional absorption of ingested lead by young children are warranted. Further investigations are especially needed in younger children than those who were subjects in the current study, particularly children in the 1-3-year-old age range. In addition, the effect of nutritional status and patterns of food intake on children's lead absorption require investigation, particularly given the increased prevalence of marginal nutritional status among low-income populations that are at increased risk of elevated blood lead levels.

Adult↗
PubMed1997

Lead exchange in teeth and bone--a pilot study using stable lead isotopes.

Stable lead isotopes and lead concentrations were measured in the enamel and dentine of permanent (n = 37) and deciduous teeth (n = 14) from 47 European immigrants to Australia to determine whether lead exchange occurs in teeth and how it relates to lead exchange in bone. Enamel exhibits no exchange of its European-origin lead with lead from the Australian environment. In contrast, dentine lead exchanges with Australian lead to the extent of approximately 1% per year. In one subject, trabecular bone from the tooth socket exchanged almost all its European lead with Australian lead over a a 15-year period (turnover of approximately 6% per year), similar to the approximately 8% per year proposed for lead turnover in trabecular bone. The repository characteristics of intact circumpulpal dentine were investigated by analyses of four sets of contiguous slices from six teeth: 1) a set consisting of slices with intact circumpulpal dentine and cementum; 2) a set in which these areas were removed; 3) another set consisting of slices with intact circumpulpal dentine and cementum; and 4) a set without cementum. These analyses show relatively small differences in isotopic composition between contiguous slices except that circumpulpal dentine appears to be the dominant control on lead concentration. There is a significant correlation (R2 = 0.19, p = 0.01, n = 34) of dentine lead concentration and rate of exchange with residence time from the country of origin and Australian lead, but there is no such correlation with enamel lead concentration. Analyses of permanent and deciduous teeth of subjects from other countries who have resided in Australia for varying lengths of time should resolve some of the questions arising from this pilot study.

Adult↗
PubMed1997

Stable lead isotopes in teeth as indicators of past domicile--a potential new tool in forensic science?

A pilot study using stable lead isotope analyses has shown that permanent and deciduous teeth from Eastern and Southern European subjects have completely different lead isotopic compositions to those of Australian subjects. There are statistically significant differences between groups of teeth from subjects from the former Soviet Union (CIS), the former Yugoslavia, United Kingdom, and Lebanon. The isotopic analyses confirm the stability of lead in enamel but suggest that there is exchange of European lead with Australian lead in dentine amounting to about 1% per year. The isotopic differences in, and exchange of, European lead and Australian lead offer an exciting and powerful tool for forensic identification.

Adult↗
PubMed1996

Importance of monitoring family members in establishing sources and pathways of lead in blood.

High precision lead isotope measurements were undertaken to establish the sources and pathways in blood and environmental samples of five families from the Broken Hill lead mining community, New South Wales, Australia. The five families were selected from 27 families investigated to illustrate the different sources and pathways of lead into blood and the importance of monitoring the whole family. The results illustrate that although the major source of lead is from the orebody, paint and petrol can be significant contributors to both house dust and blood leads. The results also show that the sources and pathways can be from the father's occupation and hence monitoring of families is important, especially in high risk locations. In two cases, the elevated blood leads in the children did not derive from their current residence but from other residences in the community.

Adult↗
PubMed1996

Non-orebody sources are significant contributors to blood lead of some children with low to moderate lead exposure in a major lead mining community.

High precision lead isotope ratios in blood from 58 children aged 1-11 years from the Broken Hill lead mining community have been measured to determine the source and pathways of lead in their blood. Sources of lead are from the Pb-Zn-Ag orebody (lead), from paint and from petrol. Thirty-five of the 58 children (60%) had blood leads (PbB) > or = 0.72 micromol/l (15 microg/dl), the current level of 'personal exposure and source remediation/abatement' compared with a 'background' level of approximately 0.29 micromol/l (6 microg/dl), estimated from adult females who were generally mothers of the children. Six of 17 children aged 7 years or older, had PbBs > or = 0.72 micromol/l (15 microg/dl). Even though the orebody lead is the major contributor to PbB in Broken Hill children, of the 35 children whose PbB is > or = 0.72 microm/l (15 microg/dl), 12 (34%) have approximately 50% or more of their PbB derived from sources such as paint and petrol or both by isotopic identification. The identification of elevated PbB in older children is a concern, especially for females, as there is potential for release of endogenous lead during pregnancy and lactation.

Child↗
PubMed1996

Tooth analyses of sources and intensity of lead exposure in children.

The sources and intensity of lead exposure in utero and in early childhood were determined using stable lead isotopic ratios and lead concentrations of incisal and cervical sections of deciduous teeth from 30 exposed and nonexposed children from the Broken Hill lead mining community in Australia. Incisal sections, consisting mostly of enamel, generally have low amounts of lead and isotopic compositions consistent with those expected in the mother during pregnancy. Cervical sections, consisting mostly of dentine with secondary dentine removed by resorption and reaming, generally have higher amounts of lead than the enamel and isotopic compositions consistent with the source of postnatal exposure. There are statistically significant differences in lead concentrations between incisal and cervical sections, representing within-tooth variation, for children with low and high lead exposure (p = 0.0007, 2 x 10(-6), respectively) and for those who have ingested leaded paint (p = 0.009). Statistically significant differences between incisal and cervical sections in these three exposure groups are also exhibited by the three sets of lead isotope ratios (e.g., p = 0.001 for 206Pb/204Pb ratio in the low exposure group). There are statistically significant differences between the low and high lead exposure groups for lead concentrations and isotopic ratios in incisal (p = 0.005 for lead concentration and 6 x 10(-6) for 206Pb/204Pb ratio) and cervical sections (p = 5 x 10(-5) for lead concentration and 6 x 10(-6) for 206Pb/204Pb ratio). The dentine results reflect an increased exposure to lead from the lead-zinc-silver mineral deposit (orebody lead) during early childhood, probably associated with hand-to-mouth activity. Leaded paint was identified as the source of elevated tooth lead in at least two cases. Increased exposure to lead from orebody and paint sources in utero was implicated in two cases, but there was no indication of previous exposure from the mothers' current blood leads, suggesting an acute rather than a chronic exposure for the mothers. Permanent teeth from one subject had lower amounts of lead in the roots compared with the crowns, and the isotopic composition of the crowns were consistent with the data for the deciduous teeth from the same subject. Based on changes in the isotopic composition of enamel and dentine, it is provisionally estimated that lead is added to dentine at a rate of approximately 2-3% per year.

Australia↗
PubMed1995

Paint as a source of recontamination of houses in urban environments and its role in maintaining elevated blood leads in children.

A detailed lead isotopic and scanning electron microscope investigation of particulates from three houses in urban Sydney, previously decontaminated by their owners, has shown that they have been recontaminated over varying periods, as short as 6 months. The source of recontamination is lead paint from adjoining dwellings whose paint is thoroughly deteriorated, as well as from unknown sources. In one house, the external to internal lead loading was > 10:1. The pathway for the lead paint contaminants is both airborne and mechanical transport into the houses. Recontamination of houses provides an explanation for the maintenance of elevated blood lead levels in the children residing in these houses. Recontamination can be a major urban problem applicable in any community which used leaded paints on dwellings in the past. It is a matter of concern for families with young children and couples, especially women who are, or intend to become, pregnant.

Air Pollutants↗
PubMed1995

Contribution of tissue lead to blood lead in adult female subjects based on stable lead isotope methods.

Public health and medical recommendations on prevention of lead toxicity rely on use of blood lead concentrations to assess lead exposure and predict onset of adverse health effects. Blood lead levels have generally been thought to reflect recent environmental lead exposures. However, tissue lead stores are accumulated over a long time period (i.e., years). These tissue stores, primarily from bone, can be remobilized as part of both normal physiologic and pathologic processes. Although chemical analyses do not differentiate lead isotopes, mass spectrometric determinations can differentiate the quantities of stable lead isotopes present in particular samples (e.g., lead 207, lead 206, lead 204, and lead 208). Selected geographic locations may have distinct isotopic profiles. For example, on mainland Australia the 206Pb/204Pb ratios reported in both environmental lead sources and blood samples are typically less than 17.0. By contrast, stable lead isotope profiles in blood samples of adult women immigrating from Eastern Europe and the former Soviet Union usually have 206Pb/204Pb ratios greater than 17.5 and as high as 18.5 on entry into Australia. Longitudinal monitoring of blood samples to determine stable lead isotope profiles by mass spectrometry and chemical analyses of blood samples for total lead content were conducted over a 300-day period. These data show that between 45% and 70% of lead in blood comes from long-term tissue lead stores. Recognition that the predominant source of lead in blood was tissue stores rather than the contemporaneous environment should greatly modify recommendations on use of blood lead to monitor occupational or environmental interventions. In addition, internal biokinetics of lead, documented through presence of tissue lead in blood, underlie the long-term health risks of lead exposure. Transfer of lead to the fetus from maternal tissue stores represents a special area of concern.

Adult↗
PubMed1994

Percutaneous absorption of inorganic lead compounds.

In vivo experiments with the stable lead isotope, 204Pb, have confirmed that inorganic lead compounds can be absorbed through the skin. Three different analytical techniques--thermal ionization mass spectrometry, inductively coupled plasma mass spectrometry and anodic stripping voltammetry--showed that lead, as lead nitrate or lead acetate, was rapidly absorbed through the skin and detectable in sweat, blood and urine within 6 h of skin application. Of the 4.4 mg of lead applied to the skin in one experiment, 1.3 mg was absorbed within 24 h. Initial rapid uptake was probably via sweat glands and hair follicles, followed by slower absorption via the transepidermal route. While increases in 204Pb concentration and abundance were observed, no increase in total lead in blood or urine was found. It is possible that the physicochemical form of skin-absorbed lead partitions strongly into extracellular fluid, but has a low affinity for erythrocytes. There was no significant difference in uptake of lead into erythrocytes (in vitro) from normal saline, synthetic sweat or sauna sweat. Ultrafiltration of sweat showed that up to 70% of lead in sweat was associated with > 30,000 MW particles. It is possible that percutaneous absorption of lead could contribute significantly to lead body burden, particularly from occupational exposure to lead in dust. Moreover, because lead absorbed through the skin was only just detectable in blood, and blood lead is the main criterion by which industry determines exposure, skin-absorbed lead may remain undetected.

Humans↗
PubMed1994

Effect of plumbing systems on lead content of drinking water and contribution to lead body burden.

Stable lead isotopes and lead contents in drinking water from a number of Australian cities have been measured to determine the contribution of drinking water to body burden. Lead contents are generally < 2 micrograms/l and thus contribute an insignificant amount to the lead budget in humans in Australia. First-flush and running water samples taken at intervals of up to 10 min show that equilibrium is reached within 1 min or approximately 10 l by volume. There is, however, large variability in both lead content and isotopic composition within the first minute which brings into question the reliability of the recommended sampling time of 30 s. Extremely large isotopic differences between individual dwellings within the one city and between dwellings and the storage tanks for the water supply are attributed to differences in lead residing in the plumbing within the dwellings, usually from lead solder in brass fittings. Isotopic analysis of solder and water from two dwellings confirm this relationship.

Australia↗
PubMedDate not supplied

Lead bioavailability in the environment of children: blood lead levels in children can be elevated in a mining community.

Lower blood lead averages in mining communities, compared with other child exposure settings, e.g., innercity areas of the United States and smelter communities, have been attributed to lower bioavailability of lead to children in the mining areas. Direct supporting evidence of the lower bioavailability has, however, generally been lacking. Elevated blood lead levels for approximately 85% of children with > 10 micrograms/dl have been reported from the Broken Hill mining community in Australia. Lead isotope, optical, and scanning electron microscope analyses on the lead species from soils and dusts show them to be derived mainly from weathered ore body material. Solubility tests using 0.1M HCl on the -53 + 38 microns fraction of soil and dust show the lead species to have a high degree of bioavailability. Ingestion of soil and dust, either directly or via mouthing activity, is the main source and pathway for elevated blood lead in children from this community.

Australia↗