Howard W. Mielke

Lead Concentrations in Inner-City Soils as a Factor in the Child Lead Problem.

Soil samples were randomly collected from 422 vegetable gardens in a study area centered in downtown Baltimore, Maryland, and having a radius of 48.28 km (30 miles). The levels of lead, four other metals (cadmium, copper, nickel, and zinc), and pH were measured for each location. The application of multi-response permutation procedures, which are compatible with mapping techniques, reveals that lead (as well as cadmium, copper, nickel, and zinc) is concentrated and ubiquitous within the soils of the inner-city area of Metropolitan Baltimore. The probability values that the concentration of metals occurred by chance alone vary from about 10(-15) to 10(-23) depending on the metal considered. Our findings pose environmental and public health issues, especially to children living within the inner-city.

Seasonality and Children's Blood Lead Levels: Developing a Predictive Model Using Climatic Variables and Blood Lead Data from Indianapolis, Indiana, Syracuse, New York, and New Orleans, Louisiana (USA)

On a community basis, urban soil contains a potentially large reservoir of accumulated lead. This study was undertaken to explore the temporal relationship between pediatric blood lead (BPb), weather, soil moisture, and dust in Indianapolis, Indiana; Syracuse, New York; and New Orleans, Louisiana. The Indianapolis, Syracuse, and New Orleans pediatric BPb data were obtained from databases of 15,969, 14,467, and 2,295 screenings, respectively, collected between December 1999 and November 2002, January 1994 and March 1998, and January 1998 and May 2003, respectively. These average monthly child BPb levels were regressed against several independent variables: average monthly soil moisture, particulate matter < 10 μm in diameter (PM10), wind speed, and temperature. Of temporal variation in urban children’s BPb, 87% in Indianapolis (R2 = 0.87, p = 0.0004), 61% in Syracuse (R2 = 0.61, p = 0.0012), and 59% in New Orleans (R2 = 0.59, p = 0.0000078) are explained by these variables. A conceptual model of urban Pb poisoning is suggested: When temperature is high and evapotranspiration maximized, soil moisture decreases and soil dust is deposited. Under these combined weather conditions, Pb-enriched PM10 dust disperses in the urban environment and causes elevated Pb dust loading. Thus, seasonal variation of children’s Pb exposure is probably caused by inhalation and ingestion of Pb brought about by the effect of weather on soils and the resulting fluctuation in Pb loading.

PAH and metal mixtures in New Orleans soils and sediments

The purpose of this study is to determine the degree of PAH contamination and the association of PAHs with inorganic substances in soils and sediments of New Orleans. Bonnet Carré Spillway (BCS) (n = 5) provides modern baseline data, while urban soil samples (CTY) (n = 27) and sediment samples from Bayou St. John (BSJ) (n = 11) provide experimental data for New Orleans. Soil samples were collected from the top 2.5 cm of the surface, air-dried, and sieved (2 mm). Sediments samples were collected with a Wildco-Ekman bottom dredge, air-dried and finely ground. Accelerated solvent extraction (ASE) was used to release PAHs from the samples and analysis was conducted with gas chromatography-mass spectrometry (GC-MS). Metals were extracted using a 5:1 ratio of 1 mol/L nitric acid (room temperature) for soil and sediment samples, shaken for 2 h, centrifuged (1000 x g for 15 min) and filtered. Metal analysis was done by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Mann-Whitney tests show PAH differences (P < 0.001). Ranking of total PAHs is, BSJ sediments (10.3 mg/kg) > CTY soils (3.7 mg/kg) > BCS alluvium (0.28 mg/kg). The sum of the metals are similar for BSJ sediments (698 mg/kg) and CTY soils (679 mg/kg) and significantly lower for BCS (189 mg/kg). Manganese of these samples is similar for each site. For paired samples, Pearson Product Moment Correlation tests reveal that many PAHs are strongly associated with each other at all locations. For BCS alluvium and BSJ sediments, total PAHs are not significantly associated with total metals. For CTY, most pairs of metals are significantly associated, and total soil PAHs are strongly associated with total soil metals (correlation 0.78, P = 4.9 x 10(-4)). The linear model, total soil PAH = 136.3 + 6.25 (total soil metals) forms the basis for a predicted PAH map of New Orleans. Previous empirical research demonstrates an association between soil lead and childrens lead exposure. This study indicates that PAHs are part of the soil mixture of accumulated substances and by-products of industrial society that presents exposure potential in cities.

PAHs and metals in the soils of inner-city and suburban New Orleans, Louisiana, USA

Representative soil samples of an inner-city and suburban community (n = 19 each) are evaluated for 16 polycyclic aromatic hydrocarbons-PAHs (naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, chrysene, benzo[k]fluoranthene, benzo[j]fluoranthene, benzo(a)pyrene, indeno[1,2,3-cd]pyrene, dibenz[a,h]anthracene and benzo[g,h,i]perylene) and nine metals (Pb, Zn, Cd, Mn, Ni, Cu, Cr, Co and V). Surface (2.5cm deep) samples were air-dried and sieved (2mm USGS #10). Accelerated solvent extraction was used for PAH preparation prior to analysis with gas chromatography-mass spectrometry. Metals were extracted at a 5:1 ratio of 1mol nitric acid to soil, shaken at room temperature, centrifuged, filtered and analyzed by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Total PAHs (median 2927ngg(-1) versus 731ngg(-1)) and the total metals (median 1323μgg(-1) versus 183μgg(-1)) summarize differences (P < 0.0001) between the inner-city and suburb, respectively. A strong association exists between PAHs and metals for all 38 soil samples (correlation coefficient = 0.831, P < 0.00001). In terms of the specific sites of accumulation, both PAHs and metals show the same pattern: busy streets > foundations > residential streets > open areas. This study provides real-world data about various chemical mixtures which may be a factor of possible health disparities in sensitive populations, especially children, in different communities of New Orleans.

Estimation of leaded (Pb) gasoline's continuing material and health impacts on 90 US urbanized areas

The subject of this paper is lead (Pb) additives in gasoline and their material and health impact from Pb dust inputs into 90 US urbanized areas (UAs). The mass of Pb additives for 90 UAs as a total of the US Pb additives in 1982 were estimated from vehicle travel, vehicle fuel economy (miles/gallon), ratio of leaded to unleaded fuel, and Pb/gallon. About 500 billion (10⁹) miles of travel in 90 UAs during 1982 account for ~18,000 metric tons (MT), or nearly 30% of the US Pb additives in 1982. Applying the 1982 proportions to the 90 UAs for 1950 through 1982 fuel sales by state accounts for ~1.4 million MT Pb of the US national total of 4.6 million MT during the same years. Fates of Pb additives in engine systems were used to calculate Pb aerosol inputs into the 90 UAs. The inputs range from 100s to more than 100,000 MT of Pb depending on a given UAs traffic flow patterns. Soils are the reservoir of urban Pb dust. The median background soil Pb for the US is 16.5mg/kg (range 10.3 to 30.1mg/kg), and less by an order of magnitude or more than soil Pb within larger UAs. Recognizing the US input of massive gasoline Pb additives into UAs assists with comprehending soil Pb differences between large and small UAs, inner and outer areas of UAs, health disparities, and school achievement issues within UAs. The findings underscore the need for controlling accumulated exterior urban Pb dust from gasoline additives along with paint sources that have accumulated in soil to meet the goal of primary childhood Pb exposure prevention.

The urban rise and fall of air lead (Pb) and the latent surge and retreat of societal violence

We evaluate air Pb emissions and latent aggravated assault behavior at the scale of the city. We accomplish this by regressing annual Federal Bureau of Investigation aggravated assault rate records against the rise and fall of annual vehicle Pb emissions in Chicago (Illinois), Indianapolis (Indiana), Minneapolis (Minnesota), San Diego (California), Atlanta (Georgia), and New Orleans (Louisiana). Other things held equal, a 1% increase in tonnages of air Pb released 22 years prior raises the present period aggravated assault rate by 0.46% (95% CI, 0.28 to 0.64). Overall our model explains 90% of the variation in aggravated assault across the cities examined. In the case of New Orleans, 85% of temporal variation in the aggravated assault rate is explained by the annual rise and fall of air Pb (total=10,179 metric tons) released on the population of New Orleans 22 years earlier. For every metric ton of Pb released 22 years prior, a latent increase of 1.59 (95% CI, 1.36 to 1.83, p<0.001) aggravated assaults per 100,000 were reported. Vehicles consuming fuel containing Pb additives contributed much larger quantities of Pb dust than generally recognized. Our findings along with others predict that prevention of childrens lead exposure from lead dust now will realize numerous societal benefits two decades into the future, including lower rates of aggravated assault.

Children's blood lead and standardized test performance response as indicators of neurotoxicity in metropolitan New Orleans elementary schools

This study analyzes pre-Katrina variation in aggregate student performance and childrens blood lead (BPb) in 117 elementary school districts in metropolitan New Orleans. Fourth grade student achievement on Louisiana Educational Assessment Program (LEAP) tests were analyzed as a function of BPb for children 1-6 years old within school districts, controlling for student-teacher ratios, percent of students eligible for a free or discounted lunch, and school racial demography. Measures of performance across subject areas (English Language Arts, Science, Mathematics, and Social Studies) include school Achievement Test Scores (ATS) and indices of agreement and variation in student achievement. ATS are measured on a 5-point scale, corresponding to achievement categories of advanced=5 to unsatisfactory=1. Regression results show that median BPb (microg/dL) and percent of children with BPb > or =10 microg/dL are significantly associated with reductions in test scores across all subjects and depress variation in student performance across achievement categories. These data suggest that assisting children with improved school performance requires alleviation of pre-school Pb exposure and its associated neurotoxic damage. Cost-benefit calculations suggest that it is more cost effective to pay for onetime primary prevention instead of paying continuous expenses focused on reversing neurotoxic damage.

Determination of Polycyclic Aromatic Hydrocarbons and Trace Metals in New Orleans Soils and Sediments

Soil and sediment samples from New Orleans have been collected and analyzed for contamination by 16 polycyclic aromatic hydrocarbons (PAHs) and 8 trace metals. Total PAH contents were found to vary from 40 μ g/kg to 40,000 μ g/kg, and concentrations of total metals varied in the range of 80 mg/kg and 7600 mg/kg. Source analysis of PAHs using diagnostic concentration ratios such as phenanthrene/anthracene and fluoranthene/ pyrene indicated that PAHs found at elevated concentrations in New Orleans soils and sediments were of pyrolytic origins. Spearman rank bivariate correlation analysis revealed significant correlations between soil PAHs and metals (r = 0.80, p < 0.0001) and between sediment PAHs and metals (r = 0.62, p < 0.05), suggesting common pollution sources for the two groups of environmental pollutants. Strong correlations were also found between Pb and Zn in soils (r = 0.93, p < 0.0001) as well as in sediments (r = 0.65, p < 0.05).

Influence of fertilizer and sewage sludge compost on yield and heavy metal accumulation by lettuce grown in urban soils

Previous research has demonstrated that many urban soils are enriched in Pb, Cd and Zn. Culture of vegetable crops in these soils could allow transfer of potentially toxic metals to foods. ‘Tanya’ lettuce (Lactuca sativa L.) was grown in pots of five urban garden soils and one control agricultural soil to assess the effect of urban-soil metal enrichment, and the effect of soil amendments, on heavy metal uptake by garden vegetables. The amendments included NPK fertilizer, limestone, Ca(H2PO4)2, and two rates of limed sewage sludge compost. Soil Cd ranged from 0.08 to 9.6 mg kg−1; soil Zn from 38 to 3490 mg kg−1; and soil Pb from 12 to 5210 mg kg−1. Lettuce yield on the urban garden soils was as great as or greater than that on the control soil. Lettuce Cd, Zn and Pb concentrations increased from 0.65, 23, and 2.2 mg kg−1 dry matter in the control soil to as high as 3.53, 422 and 37.0 mg kg−1 on the metal-rich urban garden soils. Adding limestone or limed sewage sludge compost raised soil pH and significantly reduced lettuce Cd and Zn, while phosphate fertilizer lowered soil pH and had little effect on Zn but increased Cd concentration in lettuce. Urban garden soils caused a significant increase in lettuce leaf Pb concentration, especially on the highest Pb soil. Adding NPK fertilizer, phosphate, or sludge compost to two high Pb soils lowered lettuce Pb concentration, but adding limestone generally did not. On normally fertilized soils, Pb uptake by lettuce was not exceptionally high until soil Pb substantially exceeded 500 mg kg−1. Comparing garden vegetables and soil as potential sources of Pb risk to children, it is clear that the risk is greater through ingestion of soil or dust than through ingestion of garden vegetables grown on the soil. Urban dwellers should obtain soil metal analyses before selecting garden locations to reduce Pb risk to their children.

Lead dust contaminated U.S.A. communities: comparison of Louisiana and Minnesota

Lead from gasoline has played a major role in the geochemical distribution patterns of Pb within U.S. cities. Since 1950, ~75,000 and 89,000 t of Pb were consumed as a gasoline additive in Louisiana and Minnesota, respectively. Previously, a survey was conducted in five cities in Minnesota that showed a relation between soil Pb and city size. New empirical data are presented on the geochemical pattern of Pb in soils within six cities of Louisiana. Soils were collected from within 1 m of the sides (foundations) of residences, within 1 m of the street, and from open spaces (yards or parks) within each city. The data show that soil Pb is a function of city size and that the inner city of the largest town had the highest Pb accumulation. Remarkable statistical differences (exact p-values as low as 10−80) between street-side soils of central New Orleans and adjacent communities, and other cities of Louisiana, were demonstrated. The Louisiana results are similar to those of five cities in Minnesota. The median of foundation and street-side soil samples within inner city communities of New Orleans and Minneapolis were >840 and 265 ppm Pb, respectively, whereas the median soil Pb for foundations and street-sides of the small towns of Natchitoches, Louisiana, and Rochester, Minnesota, were <50 and 58 ppm Pb, respectively.