Spatial-temporal association of soil Pb and children's blood Pb in the Detroit Tri-County Area of Michigan (USA).

Lead is a well-known toxicant associated with numerous chronic diseases. Curtailing industrial emissions, leaded paint, lead in food, and banning highway use of leaded gasoline effectively decreased children's exposure. In New Orleans, irrespective of Hurricane Katrina flooding, lead declined concurrently in topsoil and children's blood. We postulate that topsoil lead and blood lead decreases are associated and common in U.S. cities. This study tests that concept. A small 2002 soil lead survey of 8 Detroit Tri-County Area census tracts was repeated in October 2019. Between 2002 and 2019, Detroit median soil lead decreased from 183 to 92 mg/kg (or 5.4 mg/kg/yr.) and declined in Pontiac from 93 to 68 mg/kg (or 1.4 mg/kg/yr.). Median soil lead remained ~10 mg/kg in outlying communities. Median soil lead (in mg/kg) in communities at < 21 km compared to ≥ 21 km from central Detroit, respectively, decreased from 183 to 33 (P-value 10-12) in 2002 and from 92 to 35 (P-value 10-07) in 2019. Children's lead exposures were highest in Detroit (population 0.7 million in 2010) and lower by more than half in Pontiac (population 60 thousand in 2010). Between 2002 and 2018, children with blood lead ≥4.5 µg/dL in Detroit declined from 44% to 5%, and in Pontiac from 17% to 2%. The most vulnerable children live in the most lead contaminated communities. To meet the goal of primary prevention for children, along with other efforts, this study supports landscaping with low lead soil to reduce exposure in lead contaminated communities.

The concurrent decline of soil lead and children's blood lead in New Orleans.

Lead (Pb) is extremely toxic and a major cause of chronic diseases worldwide. Pb is associated with health disparities, particularly within low-income populations. In biological systems, Pb mimics calcium and, among other effects, interrupts cell signaling. Furthermore, Pb exposure results in epigenetic changes that affect multigenerational gene expression. Exposure to Pb has decreased through primary prevention, including removal of Pb solder from canned food, regulating lead-based paint, and especially eliminating Pb additives in gasoline. While researchers observe a continuous decline in children's blood lead (BPb), reservoirs of exposure persist in topsoil, which stores the legacy dust from leaded gasoline and other sources. Our surveys of metropolitan New Orleans reveal that median topsoil Pb in communities (n = 274) decreased 44% from 99 mg/kg to 54 mg/kg (P value of 2.09 × 10-08), with a median depletion rate of ∼2.4 mg⋅kg⋅y-1 over 15 y. From 2000 through 2005 to 2011 through 2016, children's BPb declined from 3.6 µg/dL to 1.2 µg/dL or 64% (P value of 2.02 × 10-85), a decrease of ∼0.2 µg⋅dL⋅y-1 during a median of 12 y. Here, we explore the decline of children's BPb by examining a metabolism of cities framework of inputs, transformations, storages, and outputs. Our findings indicate that decreasing Pb in topsoil is an important factor in the continuous decline of children's BPb. Similar reductions are expected in other major US cities. The most contaminated urban communities, usually inhabited by vulnerable populations, require further reductions of topsoil Pb to fulfill primary prevention for the nation's children.

Associations between standardized school performance tests and mixtures of Pb, Zn, Cd, Ni, Mn, Cu, Cr, Co, and V in community soils of New Orleans.

In New Orleans a strong inverse association was previously identified between community soil lead and 4th grade school performance. This study extends the association to zinc, cadmium, nickel, manganese, copper, chromium, cobalt, and vanadium in community soil and their comparative effects on 4th grade school performance. Adjusting for poverty, food security, racial composition, and teacher-student ratios, regression results show that soil metals variously reduce and compress student scores. Soil metals account for 22%-24% while food insecurity accounts for 29%-37% of variation in school performance. The impact on grade point averages were Ni > Co > Mn > Cu ~ Cr ~ Cd > Zn > Pb, but metals are mixtures in soils. The quantities of soil metal mixtures vary widely across the city with the largest totals in the inner city and smallest totals in the outer city. School grade point averages are lowest where the soil metal mixtures and food insecurity are highest.

Analysis of trend: a permutation alternative to the F test.

When the categories of the independent variable in an analysis of variance are quantitative, it is more informative to evaluate the trends in the treatment means than to simply compare differences among the treatment means. A permutation alternative to the conventional F test is shown to possess significant advantages when analyzing trend among quantitative treatments in a one-way analysis of variance. An example with and without an extreme data point illustrates the effectiveness of the permutation alternative for the analysis of trend when homogeneity of variance is compromised.

Maximum-corrected and chance-corrected measures of effect size for the Mantel-Haenszel test.

Two measures of effect size are described for the Mantel-Haenszel test. Both measures belong to the r-family of effect size measures. One measure is based on a maximum-corrected model, and the second measure is based on a chance-corrected model.

Multiway contingency tables: Monte Carlo resampling probability values for the chi-squared and likelihood-ratio tests.

Monte Carlo resampling methods to obtain probability values for chi-squared and likelihood-ratio test statistics for multiway contingency tables are presented. A resampling algorithm provides random arrangements of cell frequencies in a multiway contingency table, given fixed marginal frequency totals. Probability values are obtained from the proportion of resampled test statistic values equal to or greater than the observed test statistic value.

Stuart's tau measure of effect size for ordinal variables: some methodological considerations.

The reporting of measures of effect size has become increasingly important in psychology. A Monte Carlo resampling permutation procedure is introduced to find near-optimum maximum values for Stuart's tau(c) measure for two-way ordinal contingency tables, also termed Kendall's tau(c) since Kendall introduced tau(a) and tau(b). Comparisons between resampling and exact procedures demonstrate the accuracy and utility of resampling measures of effect size for two-way ordinal contingency tables. The resampling procedure is shown to be more precise than the traditional method of standardizing tau(c).

Nominal-ordinal measures of association: a comparison of two measures.

The measurement of the magnitude of association between a nominal independent variable and an ordinal dependent variable is an important, but neglected, component in psychological research. Two measures of nominal-ordinal association are described and compared. Resampling permutation methods are utilized to compute probability values for both measures.

Resampling permutation probability values for Cronbach's alpha.

A permutation procedure to compute a resampling probability value and empirical quantile limits is provided for Cronbach's alpha measure of internal reliability. The underlying assumptions for the conventional use of alpha are discussed. The use of a permutation test for Cronbach's alpha is highlighted as a valuable tool when sample sizes are small and necessary assumptions cannot be met.

Resampling permutation probability values for weighted kappa.

A permutation algorithm and associated FORTRAN program are provided for resampling weighted kappa. Program RWK provides the weighted kappa test statistic and the resampling one-sided upper-tail probability value.

Resampling probability values for weighted kappa with multiple raters.

A new procedure to compute weighted kappa with multiple raters is described. A resampling procedure to compute approximate probability values for weighted kappa with multiple raters is presented. Applications of weighted kappa are illustrated with an example analysis of classifications by three independent raters.

Exact permutation probability values for weighted kappa.

A permutation algorithm and associated FORTRAN program are provided for weighted kappa. Program EWK provides the weighted kappa test statistic and the exact one-sided upper-tail probability values.

Weighted kappa for multiple raters.

Five procedures to calculate the probability of weighted kappa with multiple raters under the null hypothesis of independence are described and compared in terms of accuracy, ease of use, generality, and limitations. The five procedures are (1) exact variance, (2) resampling contingency, (3) intraclass correlation, (4) randomized block, and (5) resampling block. While each procedure possesses strengths and limitations, the resampling contingency procedure is shown to be the most versatile and accurate of the five procedures, provided the number of raters is not too large. The resampling contingency procedure permits any weighting scheme, accommodates both symmetrical and asymmetrical weights, is suitable for both weighted and unweighted kappa, and makes no assumptions about either the data distribution or the probability distribution.

Resampling programs for multiway contingency tables with fixed marginal frequency totals.

A resampling algorithm is presented for analyzing multiway contingency tables with fixed marginal frequency totals. Applications are illustrated with extensions of Fisher's exact, Pearson's chi-squared, and likelihood-ratio tests to three-way contingency tables.

An alternative measure of effect size for Cochran's Q test for related proportions.

Measures of effect size are increasingly important in psychological research. In this paper, a chance-corrected measure of effect size is introduced for Cochran's Q test.

Resampling permutation probability values for six measures of qualitative variation.

An algorithm and associated FORTRAN program are provided for six common measures of ordinal association: Kendall's taua and taub, Stuart's tauc, Goodman and Kruskal's gamma, and Somers' dyx and dxy. Program ROMA reports the observed data table, the values for the six test statistics, and the resampling upper- and lower-tail probability values associated with each test statistic.

A note on permutation tests of significance for multiple regression coefficients.

In the vast majority of psychological research utilizing multiple regression analysis, asymptotic probability values are reported. This paper demonstrates that asymptotic estimates of standard errors provided by multiple regression are not always accurate. A resampling permutation procedure is used to estimate the standard errors. In some cases the results differ substantially from the traditional least squares regression estimates.

Two-sample multivariate similarity permutation comparison.

A multivariate permutation test of similarity between two populations with corresponding unordered disjoint categories is described. The test statistic, resampling probability value, and measure of effect size are described.

Permutation tests: precision in estimating probability values.

The number of resamplings necessary to accurately estimate a probability value is an open question. One million resamplings is shown to be sufficient to ensure precision to three places under most conditions.

The exact variance of weighted kappa with multiple raters.

Weighted kappa described by Cohen in 1968 is widely used in psychological research to measure agreement between two independent raters. Everitt then provided the exact variance for weighted kappa for two raters. In this paper, Everitt's exact variance is extended to three or more raters.