Lead Concentrations In Soil Research Articles

Source Apportionment of Lead Contamination in Residential, Undisturbed, and Roadside Soil (Part II)

Lead (Pb) and antimony (Sb) concentrations in bulk soils and results of individual particle analysis were used to obtain apportionment estimates of identifiable sources of anthropogenic Pb contamination in residential and undisturbed soils. Soil was analyzed from residential and undisturbed wooded areas, an adjacent automobile battery manufacturing facility, and a roadside 2.4 km from the site. Sb in bulk soil was used in apportionment estimates because Sb occurred with Pb originating from the battery facility. Average Pb concentrations in roadside soil were used to obtain estimates of maximum Pb portions attributable to automobile exhaust in residential and undisturbed soils. Data from Pb-Sb-Sn particles and Pb-oxide particles provided apportionment estimates of Pb contamination similar to that derived from bulk soil concentrations. Estimates indicated most (> 80%) of the Pb contamination in residential and undisturbed wooded area soils originated from the neighboring battery facility. Less than a few percent of the Pb in the residential and undisturbed wooded area soils was naturally occurring.

Ecological risk assessment of lead contamination at rifle and pistol ranges using techniques to account for site characteristics

Spent ammunition at outdoor rifle and pistol (RP) firing ranges creates a characteristic pattern of contamination, whereby small areas surrounding backstop berms exhibit extremely high soil lead (Pb) concentrations. We characterized sources, pathways and uncertainty in contaminant accumulation for receptors at two RP ranges in southeastern Ontario. Based on these results, we performed risk calculations using kriging to estimate risk across "worst-case" species foraging ranges. Range-normalized hazard quotients (RNHQ) were then calculated to estimate risk across each receptor's foraging range. Monte Carlo simulation was used to provide +2 standard deviation (SD) risk estimates, in order to account for uncertainty in risk parameters. The American robin was found to be most at risk (RNHQ=4.10; +2SD=9.24), followed by the short-tailed shrew (RNHQ=0.113; +2SD=0.243) and the eastern cottontail (RNHQ=0.109; +2SD=0.703). Elevated risk for the American robin and short-tailed shrew was due to their small foraging ranges and habit of eating earthworms, which bioaccumulate Pb. Elevated risk for the eastern cottontail was due to vegetation accumulating Pb to levels that were considerably higher than conventional bioaccumulation models would indicate. The results of this study clearly emphasize the importance of specific characteristics of RP ranges, such as contamination patterns, dust accumulation on plant tissues, and contaminant bioaccessibility. These characteristics should be accounted for, not only in performing risk assessments, but also in choosing remedial options and in routine management practices.

Potential lead on play surfaces: Evaluation of the “PLOPS” sampler as a new tool for primary lead prevention

This New Orleans study tested the “potential lead on play surfaces” (PLOPS) sampler, as a tool for measuring the potential lead (Pb) surface loading per area (e.g., μg/ft 2) of the soil. The PLOPS is a cylindrical vinyl envelope filled with 1 kg (2.2 lbs) water. A wet wipe, the same type as used for floor wipes, is clipped to the bottom of the cylindrical vinyl envelope and placed on the soil and turned one quarter of a turn and back to obtain a sample. PLOPS samples paired with one conventional soil lead (SL) sample (amount of Pb per mass) up to 2.5 cm (1 in) deep were collected from 25 properties and 67–69 field sites before and after covering them with clean Mississippi River alluvial soil from the Bonnet Carré Spillway (BCS). Permutation methods were used to evaluate results. The correlation was 0.85 between Plops 1 and 2 and the agreement was 0.79 ( P-values⪡0.0000001, i.e., extreme). The averages of PLOPS duplicates were used to correlate PLOPS and SL. The simplest mathematical expressions are in the forms y = a + b x c and x = d + e y f , where x is PLOPS and y is SL. The results were: y=−7.42+0.408 x 0.97 and x=−43.74+24.85 y 0.69. The agreements were 0.61 and 0.62, respectively ( P-value⪡0.0000001). According to the relationship, when the PLOPS measure 40 μg/ft 2, the predicted SL is 7.2 mg/kg. Also, when SL measures 400 mg/kg, 1508 μg/ft 2 is predicted for PLOPS; therefore, SL concentration underestimates the potential for Pb exposure from the soil surface. The PLOPS tool provides a measurement that is comparable with interior floor wipes because it measures the amount of Pb per area a child is likely to encounter while at play on the soil surface.

Study of the Transfer Coefficient of Cadmium and Lead in Ryegrass and Lettuce

The aim of study was to find the correlation between the concentration of the total amount of heavy metals of soils and that of plants because it shows which elements can be accumulated by different plants. The transfer coefficient is the metal concentration in plant tissues aboveground divided by the total metal concentration of soil. Pot experiments were conducted under greenhouse conditions. The total lead (Pb) content (about 21 mg · kg−1 soil) of soils was higher than the cadmium (Cd) content (about 0.21 mg · kg−1 soil). The Cd concentration of lettuce (averaging 0.93 mg · kg−1) was higher than that of ryegrass (averaging 0.20 mg · kg−1). The transfer coefficient of Cd was lower in ryegrass (averaging 0.95) than in lettuce (4.47). In this experiment, the concentration of Cd was almost five times higher in the four‐leaf lettuce than the Cd content of soil. The transfer coefficient of Pb was generally 0.064 in both plants.

Uptake and accumulation of lead by plants from the Bo Ngam lead mine area in Thailand

A field survey of terrestrial plants growing on Bo Ngam lead mine area, Thailand, was conducted to identify species accumulating exceptionally high concentrations of lead. Plant and soil samples were collected from five areas. Lead concentrations in surface soil ranged from 325 to 142 400 mg/kg. The highest lead concentration in soil was found at the ore dressing plant area and lowest at a natural pond area. In different areas, the concentrations of lead in plants were different when comparing various study sites. A total of 48 plant species belonging to 14 families were collected from five sampling sites. Twenty-six plant species had lead concentrations more than 1000 mg/kg in their shoots. Three species ( Microstegium ciliatum, Polygala umbonata, Spermacoce mauritiana) showed extremely high lead concentrations in their shoots (12 200–28 370 mg/kg) and roots (14 580–128 830 mg/kg).

Developing a critical load approach for national risk assessments of atmospheric metal deposition

The critical load approach has been proposed for evaluation of the need to reduce atmospheric emissions of metals that lead to transboundary transport and deposition across Europe. The present study demonstrates and evaluates the application of a critical load approach for national-scale risk assessment of metal deposition in the United Kingdom. Critical load maps, calculated using critical limits based on pH-dependent free metal ion activities, are presented. Current concentrations of lead and cadmium in soils are compared with two sets of critical limit values: First, limits based on the reactive soil concentration, and second, a pH-dependent free ion critical limit function, which takes into account variable soil characteristics across the country. The use of these two models leads to different conclusions about which areas of the United Kingdom are at greatest risk, partly because of differences in the range of values of pH and organic matter in soils used in ecotoxicological experiments and in the national database. Critical loads were calculated based on free ion critical limits; the critical loads were lowest in the south and east of the country and were associated with higher soil pH, lower runoff, and lower soil organic matter.

Influence of paint chips on lead concentration in the soil of public playgrounds in Tokyo

Lead concentration in the surface soils from 31 playgrounds in a ward in Tokyo was measured to examine if paint chips, peeled off from playing equipment installed in the playgrounds, contribute to elevated Pb concentration in the soil of public playgrounds. Lead concentration in the paint chips sampled from playgrounds ranged from 0.003 to 8.9%. Lead concentration in the surface soil ranged from 15.2 to 237 mg kg(-1) (average, 55.5 mg kg(-1)) and higher Pb concentration was found in the soil near painted playing equipment indicating that paint chips from playing equipment contributed to increase soil Pb level of playgrounds in Tokyo. The degree of peeling-off of paint on the surface of playing equipment in the public playground (peeling-off index: POI) positively correlated with Pb concentration in the soil (Spearman rank-correlation coefficient, r = 0.366, p = 0.043). The stronger correlation between Pb concentration and isotope ratios (207Pb/206Pb and Pb conc., r = 0.536, p = 0.002, 208Pb/206Pb and Pb conc. r = 0.600, p < 0.001) than that between Pb and POI indicated that gasoline Pb contributed more to the playground-to-playground variation in soil Pb concentration. It was concluded that both gasoline Pb of the past and paint chips contributed to increased Pb concentration in the surface soil of playgrounds in Tokyo, though the contribution of paint chips is smaller than gasoline Pb.

Use of a geographic information system to track smelter-related lead exposures in children: North Lake Macquarie, Australia, 1991–2002

BackgroundTo determine patterns of childhood lead exposure in a community living near a lead and zinc smelter in North Lake Macquarie, Australia between 1991 and 2002.MethodsAn analysis of serial blood lead levels (BLL) of children less than 13 years of age in North Lake Macquarie participating in voluntary blood lead screening. Distance to the smelter and soil lead concentration of the child's place of residence was calculated. Categorical analysis of BLL by residential distance from smelter, residential soil lead concentration, age and year of sample was calculated. Linear regression models were fit for blood lead levels against residential distance from smelter, the log of residential soil lead concentration, age and year of BLL sample.ResultsGeometric mean BLLs were statistically significantly higher for distances less than 1.5 kilometres from the smelter and for residential soil lead concentrations greater than 300 ppm. Yearly BLLs since 1995 were statistically significantly lower than for preceding years, with an average decrease of 0.575 μg/dL per year since 1991. BLLs are statistically significantly higher for children whose age is 1 to 3 years old. Linear regression modelling of BLL predicted a statistically significant decrease in BLL of 3.0831 μg/dL per kilometre from the smelter and a statistically significant increase in BLL of 0.25 μg/dL per log of lead in residential soil. The model explained 28.2% of the variation in BLL.ConclusionResidential distance to the smelter, log of residential soil lead concentration, child's age and year of BLL sample are statistically significant factors for predicting elevated BLLs in children living near a North Lake Macquarie lead smelter.

Distribution of copper, lead, cadmium and zinc concentrations in soils around Kabwe town in Zambia

The extent of pollution of the environment as a result of mining activities in Kabwe, the provincial capital of Central province in Zambia has not yet been evaluated. Mining of lead and zinc were the core activities of Kabwe mine while cadmium and silver were produced as by-products. The smelting processes produced a significant amount of copper. The spatial distribution of four heavy metals in soils in the northern, eastern, southern and western directions of the mine was analyzed using atomic absorption spectrometry (AAS). Samples were collected up to 20 km in each direction from the mine. Results were consistent with the wind flow patterns in the town. Results ranged between 0.08 and 28 mg kg −1 (Cd); 0.20 and 0.61 mg kg −1 (Cu); 0.10 and 758 mg kg −1 (Pb) and 0.40 and 234 mg kg −1 (Zn) suggesting high precipitation of metals from the core mining activities. These concentrations were for only the fractions of metals extractable by 0.5 M nitric acid and that could be available for plant uptake in the environment. The distribution of metals indicated a decrease of metal concentrations with distance from the mine, which confirmed that precipitation due to mining activities was the main cause of soil contamination.

ENVIRONMENTAL EXPOSURE AT DAY CARE CENTRES: ARE OUR CHILDREN AT RISK?

ISEE-380 Introduction: This study aimed to characterise the exposure of 5-year old children attending pre-school facilities in Pretoria to lead (as an example of an environmental pollutant) in air and surface soil, specifically in relation to their activity patterns. Methods: The study was conducted during winter (July 2001), at 30 pre-school facilities in Soshanguve and at 24 pre-schools in Pretoria East. Questionnaires, time-activity diaries, as well as the concentrations of lead in air, surface soil and dust were statistically analysed to determine exposure to lead in air, lead concentrations in surface soil and dust, and risk factors associated with inhalation exposure to lead. Results: The study found that environmental lead levels, especially in air, were generally low. In Pretoria East, where traffic counts were higher than in Soshanguve, lead exposure to airborne lead was also significantly higher. In contrast, it was found that mean soil lead concentrations and surface dust lead loadings were higher in Soshanguve compared to those in Pretoria East. Discussion: This study found that certain features associated with a pre-school may affect the degree of exposure of children to environmental pollutants. Recommended measures which may assist in reducing the risk of exposure include locating future pre-schools away from busy roads, roads that slope steeply, or from busy crossings where traffic stops and starts, thus increasing motor vehicle emissions. It is also advisable to monitor traffic volumes on roads close to planned pre-schools in advance. Appliances used during cleaning should not disperse dust to minimize the risk of re-suspending lead and other heavy metals contained in surface dust.

Analytical Studies on Lead Pollution in Roadside Soil Samples of Raipur and Bhilai, Chhattisgarh State, India

Although lead in gasoline represents only 2.2% of total global lead use, this fuel remains by far the single largest source of this heavy metal in urban areas. In developing countries like India approximately 90% of all lead emissions into the atmosphere are due to the use of leaded gasoline. In many countries in Southeast Asia, unleaded gasoline is scarce, and the maximum allowed lead content might reach or exceed 0.8 ppm per liter. Emissions from the metallurgical operations and the waste incineration are also responsible for the rising levels of lead in the environment. Battery recycling, lead‐glazed pottery, and lead pigments industries are other sources of lead in the environment. In the present work, lead pollution in soil samples from Raipur (capital city) and Bhilai, Chhattisgarh State, India, has been investigated. The lead concentration in the surface soil of Raipur and Bhilai was found in the range of 7.2–84.0 and 9.5–79.7 ppm, respectively. The seasonal and temporal variations in the concentration of metal, its distribution pattern, and trend are discussed as well as the mobility, deposition, and sources of lead in the area. The enrichment factor of lead in the urban soil was found to be very high, depending on the nature of sources.

Changes in manganese and lead in the environment and young children associated with the introduction of methylcyclopentadienyl manganese tricarbonyl in gasoline—preliminary results

A 4-year longitudinal study is being conducted to evaluate potential changes to the environment and exposure of young children associated with the introduction of methylcyclopentadienyl manganese tricarbonyl (MMT) into Australia in 2001. The cohort consists of 57 females and 56 males, with an age range of 0.29–3.9 years. Samples are collected every 6 months from children in residences located at varying distances from major traffic thoroughfares in Sydney. Environmental samples include air, house, and daycare center dustfall, soil, dust sweepings, and gasoline; samples from the children include blood, urine, handwipes prior to and after playing outdoors, and a 6-day duplicate diet. All samples are analyzed for a suite of 20 elements using inductively coupled plasma methods. Results are presented for the first three 6-month sampling periods for lead (Pb) and manganese (Mn). For dustfall accumulation, expressed as metal concentration/m 2/30 days, there was no significant difference between homes and daycare centers for either Pb or Mn, no significant change over the three sampling periods (time) for Pb or Mn, and a positive relationship between “traffic exposure” (traffic volume and proximity to the road) and Pb but not Mn. Lead concentrations in soil was a significant predictor for Pb in the house dustfall. For handwipes, the concentrations of Pb and Mn in wipes taken from children after playing outdoors was usually significantly greater than those for wipes taken prior to playing. There was no significant association between the concentrations of either Pb or Mn in handwipes and traffic exposure, and there was no significant association between Pb concentrations in the handwipes and gender, although the latter showed a marginally significant association for Mn ( P = 0.053 ). Age was related to Pb level in the handwipes, with older subjects having higher Pb levels, and there were significant decreases in Pb and Mn concentrations over time. Dustfall accumulation was a significant predictor for Pb in the handwipes, and dust sweepings were a significant predictor of Mn in handwipes. Blood lead (PbB) concentrations ranged from 0.6 to 19 μg/dL (GM 2.6) ( n = 269 ), and manganese in blood (MnB) ranged from 1.8 to 45 μg/L (GM 11.6) ( n = 254 ). There was no significant difference between females and males for either mean PbB or MnB; over time there was a significant decline in PbB but no significant change in MnB. The only significant predictor for PbB was dustfall accumulation, although dietary intake may also be important, and the only significant predictor for MnB was Mn in handwipes prior to playing. At this early stage of the investigation we have not been able to detect any increases in Mn in these environmental samples or blood samples potentially associated with the use of MMT; in fact the Mn levels in handwipes declined over time.

Distribution of pesticides and heavy metals in trophic chain

Determination of triazines herbicides (atrazine and simazine) by high performance liquid chromatography (HPLC) in samples of trophic chain were worked out. Determination limits of 0.5 μg g −1 for atrazine, 0.8 μg g −1 for simazine with pesticides recovery of 70–77% in trophic chain samples were obtained. The content of simazine in soils was in range 1.72–57.89 μg g −1, in grass 5–88 μg g −1, in milk 2.32–15.29 μg g −1, in cereals 10.98–387 μg g −1, in eggs 30.14–59.48 μg g −1, for fruits: 2.45–6.19 μg g −1. The content of atrazine in soils was in range 0.69–19.59 μg g −1, in grass 7.85–23.85 μg g −1, in cereals 1.88–43.08 μg g −1. Cadmium, lead and zinc were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) in the same samples as atrazine and simazine. Determination limits for cadmium 5 × 10 −3 μg g −1, for lead 1 × 10 −2 μg g −1, and for zinc 0.2 × 10 −3 μg g −1, were obtained. The content of cadmium in soil was in range 0.13–5.89 μg g −1, in grass 114–627.72 × 10 −3 μg g −1, in milk 8.88–61.88 × 10 −3 μg g −1, in cereals 0.20–0.31 μg g −1, in eggs 0.11–0.15 μg g −1, in fruits 0.23–0.59 μg g −1. The content of lead in soils was in range 0.57–151.50 μg g −1, in grass 0.16–136.57 μg g −1, in milk 1.16–3.74 μg g −1, in cereals 1.05–5.47 μg g −1, in eggs 5.79–55.87 μg g −1, in fruits 21.00–87.36 μg g −1. Zinc content in soil was in range 9.15–424.5 μg g −1, in grass 35.20–55.87 μg g −1, in milk 20.00–34.38 μg g −1, in cereals 14.94–28.78 μg g −1, in eggs 15.67–32.01 μg g −1, in fruits 14.94–18.88 μg g −1. Described below extraction and mineralization methods for particular trophic chains allowed to determine of atrazine, simazine, cadmium, lead and zinc with good repeatability and precision. Emphasis was focused on liquid–liquid extraction and solid-phase extraction of atrazine and simazine from analysed materials, as well as, on monitoring the content of herbicides and metals in soil and along trophic chain. Higher concentration of pesticides in samples from west region of Poland in comparison to that of east region is likely related to common applying them in Western Europe in relation to East Europe. The content of metals strongly depends on samples origin (industry area, vicinity of motorways).

Seasonal variation in heavy metal accumulation in subtropical population of the terrestrial isopod, Porcellio laevis

The aim of the present study is to evaluate the seasonal fluctuation of heavy metals in the isopod Porcellio laevis at four uncontaminated subtropical locations. This study was carried out at four different field sites in Assiut, Egypt. The concentrations of cadmium, lead, copper, and zinc in animal, soil, and litter (μg/g dry weight) were monthly recorded during the period from June 2002 till May 2003. There was little difference in metal accumulation trends between the sites. In general, the isopod showed significant increased Pb and Zn concentration during summer and spring months, whereas this was not the case for Cd and Cu. The bioaccumulation (BAF) and bioconcentration factors (BCF) of the metals revealed marked seasonal changes throughout the year. Generally, BAF of metals were higher during summer and spring, and BCF were higher during summer and autumn. Comparing the metal accumulation with climatic fluctuations (measured) it was speculated that temperature was the main factor causing seasonal fluctuations of the internal metal concentration in the isopod.

Influence of soil lead (Pb) levels on fungal occurrence, growth and sporulation

The emission of exhaust fumes into the environment, which are eventually deposited in to soils, contributes to the increasing hazardous levels of lead in the soil ecosystem. Kenya has a high number of automotives that emit high levels of exhaust fumes that make lead a major environmental pollutant. At high levels, lead has adverse effect on the soil microbiota. This study was designed to investigate the effect of lead on mucoraceous fungi in a roadside habitat. Mucoraceous fungi are mostly saprophytes and play an important role in nutrient cycling, elemental storage and transport in the soil. Soil plate and dilution methods were used to isolate fungi from the topsoil collected from the Kiambu roadside habitat and forest stand. The soil lead content was determined by atomic absorption spectrometry. The effect of lead on the occurrence, growth and sporulation of the fungi was studied. Lead concentration of up to 160 &mu;g g-1 was recorded from the roadside, habitat soils. This decreased with increase in distance away from the road. The mucoraceous fungi showed a decline in frequency of occurrence and species diversity with increasing lead pollution load in the soil. However, Cunninghamella spp. were predominantly present in the heavily contaminated soils and showed good in vitro growth in lead agar medium. Cunninghamella. elegans, which was the most common species showed tolerance for lead. Theses results showed that lead negatively affected the occurrence and diversity of mucoraceous fungi. The presumed tolerance of lead by species of Cunninghamella presents them as candidates for use in remediation of contaminated soils. Key Words: Mucorales, soil fungi, soil contamination, lead, pollution, exhaust fumes. J. Trop. Microbiol Vol.2 2003: 27-34

A multivariate analysis of the accumulation and fractionation of major and trace elements in agricultural soils in Hidalgo State, Mexico irrigated with raw wastewater

We evaluated the accumulation and distribution of major and trace elements in agricultural soils of District 03 (DR03) in the State of Hidalgo, Mexico, irrigated with raw wastewaters for an average of 20 years. Samples of topsoils (0–30 cm depth) were extracted using a modified Tessier method. Total concentrations of the species tested were in the ranges of 675−1176 mg K kg −1, 277.9–1001 mg Na kg −1, 6,708−81,854 mg Ca kg −1, 23,800−106,974 mg Mg kg −1, 9.2−123.8 mg B kg −1, 0.6−1.9 mg Cd kg −1, 11.6−27.4 mg Cr kg −1, 3.9–47.0 mg Pb kg −1. Concentrations of As and Hg were very low. Concentrations of total Cd, Cr and Pb were generally below the maximum permissible levels set by the regulations of the European Union except for cadmium, which was in the middle of the maximum European range allowed for two soils. Regarding lead, one soil (S5) could reach the maximum permissible level of the EU in 6 more years of continued irrigation. On the other hand, contents of Pb in the most mobile fractions (“e” in this work) were significant (range: 3–28%). This distribution translated into concentrations of soluble plus exchangeable lead of approximately 2 mg Pb kg −1 in three of six soils, significantly higher than the Swiss tolerance limit of 1.0 mg Pb kg −1 for mobile fractions of lead in soils. Multivariate analysis of the data (Pearson correlation and principal component analysis) quantitatively confirmed that: (i) there is a strong covariance between boron contents and several variables representing the salinity of soils (electrolytic conductivity, a variety of alkaline and alkaline−earth total and fraction concentrations). It appears that there is a problem with high boron content in soils, although the salinity is high only for one of the soils (S3); (ii) a significant correlation among irrigation time, lead content (total, fraction easily exchangeable and bound to organic matter and sulfides) and organic carbon in soils was found; (iii) another association among irrigation time, total contents of cadmium, chromium and boron, and organic carbon was observed.

Lead tolerance in Aporrectodea rosea earthworms from a clay pigeon shooting site

Lead tolerance in individuals of the earthworm species Aporrectodea rosea collected from a clay pigeon shooting site was investigated. Lead concentrations in the shooting site soil and the un-shot control site were 6410±2250 and 296±98 mg Pb kg −1 dry weight, respectively. Of these concentrations 1050±240 and 12±9 mg Pb kg −1 dry weight were suggested to be available, using ammonium acetate (1 M), respectively. With respect to earthworm body burdens of lead the shooting site earthworms had a body burden of 6.1±1.2 mg Pb g −1 dry weight while the uncontaminated site earthworms had almost a 1000-times lower body burden of 7.1±9.0 μg Pb g −1 dry weight. Lead tolerance was assessed in uncontaminated soil that had been augmented with lead, using lead nitrate solutions, to obtain lead concentrations in soil of 0.5, 5 and 50 mg Pb kg −1 dry weight. Earthworms were exposed for 28 days during which time a semi-qualitative assessment was made of their condition. Results showed no decrease in condition in the shooting site earthworms with increasing exposure time or concentration. In contrast, earthworms collected from an uncontaminated site showed a significant ( p<0.05) decrease in condition when exposed to lead concentrations above, and including, a concentration of 5 mg kg −1 dry weight soil. These results suggested lead tolerance in the shooting site earthworms.

The Influence of Exterior Dust and Soil Lead on Interior Dust Lead Levels in Housing That Had Undergone Lead-Based Paint Hazard Control

To aid in understanding the contribution of exterior dust/soil lead to postintervention interior dust lead, a subset of housing from the HUD Lead-Based Paint Hazard Control Grant Program Evaluation was selected for study. Housing from 12 state and local governments was included. Exterior entry and street dust samples were obtained by a vacuum method, and soil samples were building perimeter core composites. Interior dust wipe lead data (μg/ft2) and paint lead data (mg/cm2) were also available for each of the dwelling units and included in the modeling. Results from 541 dwelling units revealed a wide range of exterior dust and soil lead levels, within and between grantees. Minimum and maximum geometric mean lead levels, by grantee, were 126 and 14,400 μg/ft2 for exterior entry dust; 325 and 4,610 μg/ft2 for street dust; and, for soil concentration, 383 and 2640 ppm. Geometric mean exterior entry dust lead concentration (1641 ppm) was almost four times as high as street dust lead concentration (431 ppm), suggesting that lead dust near housing was often a source of street dust lead. Geometric mean exterior entry dust lead loading was more than four times as high as window trough dust lead loading and more than an order of magnitude higher than interior entry dust lead loading. Statistical modeling revealed pathways from exterior entry dust lead loading to loadings on interior entryway floors, other interior floors, and windowsills. Paint lead was found to influence exterior entry dust lead. Results of this study show that housing where soil lead hazard control activities had been performed had lower postintervention exterior entry, interior entry floor, windowsills, and other floor dust loading levels. Soil was not present for almost half the buildings. Statistical analysis revealed that exterior strategy influenced soil lead concentration, and soil lead concentration influenced street dust lead loading. This study represents one of the few where an impact of soil treatments on dust lead levels within the housing has been documented and may represent the first where an impact on exterior entry dust lead has been found. The inclusion of measures to mitigate the role of exterior sources in lead hazard control programs needs consideration.

Lead in paddy soils and rice plants and its potential health risk around Lechang Lead/Zinc Mine, Guangdong, China

As part of a project on phytoextraction of lead (Pb) in paddy soils around a lead/zinc (Pb/Zn) Mine in Lechang of Guangdong Province, South China, the concentration distribution of Pb in paddy soil–rice system was investigated, and its potential health risk to animal/human was evaluated. Total and diethylenetetraminepentaacetic acid (DTPA)-extractable Pb in soils averaged 1486 and 268 μg/g, respectively. According to sequential extraction procedure, soil Pb occurred primarily in the residual, carbonate and exchangeable fractions (30.2%, 26.7% and 19.1%, respectively). Lead extracted by the gastric juice simulation test (GJST) was 1068 μg/g and accounted for 75.4% of the total concentration. Mean Pb concentrations of 419 μg/g in rice root, 69.1 μg/g in whole straw, 51.0 μg/g in part straw (without two leaves near above the root), 44.9 μg/g in stalk, 21.9 μg/g in hull, 13.2 μg/g in grain with hull and 4.67μg/g in grain without hull (namely, unpolished rice) were found. Lead concentrations in both soil and rice plant were far above the corresponding tolerable levels. Lead daily intakes by local residents were 2.6 mg for adults and 1.2 mg for children, which were much higher than the allowable level. Thus, Pb in this area might pose a potential health risk to the local population.

Evaluation of landscape coverings to reduce soil lead hazards in urban residential yards: The Safer Yards Project

This study was designed primarily to evaluate the effectiveness of landscape coverings to reduce the potential for exposure to lead-contaminated soil in an urban neighborhood. Residential properties were randomized in to three groups: application of ground coverings/barriers plus placement of a raised garden bed (RB), application of ground coverings/barriers only (no raised bed, NRB), and control. Outcomes evaluated soil lead concentration (employing a weighting method to assess acute hazard soil lead [areas not fully covered] and potential hazard soil lead [all soil surfaces regardless of covering status]), density of landscape coverings (6=heavy, >90% covered; 1=bare, <10% covered), lead tracked onto carpeted entryway floor mats, and entryway floor dust lead loadings. Over 1 year, the intervention groups had significantly reduced acute hazard soil lead concentration (median change: RB, −478 ppm; NRB, −698 ppm; control, +52 ppm; Kruskal–Wallis, P=0.02), enhanced landscape coverings (mean change in score: RB, +0.6; NRB, +1.5; control, −0.6; ANOVA, P<0.001), and a 50% decrease in lead tracked onto the floor mats. The potential hazard soil lead concentration and the entryway floor dust lead loading did not change significantly. Techniques evaluated by this study are feasible for use by property owners but will require continued maintenance. The long-term sustainability of the method needs further examination.