The use of analytical chemistry measurements in environmental monitoring is dependent on an asses... more The use of analytical chemistry measurements in environmental monitoring is dependent on an assessment of measurement error. This paper demonstrates the utility of a two-component error model in setting limits of detection and related concepts. The model is applicable to analytical methods in which high concentrations are measured with approximately constant relative standard deviation. At low levels, the relative standard deviation cannot stay constant, since this implies vanishingly small absolute standard deviation. The two-component model has approximately constant standard deviation near zero concentration, and approximately constant relative standard deviation at high concentrations, a pattern that is frequently observed in practice.
The contribution of subsidized food commodities to total food consumption is unknown. We estimate... more The contribution of subsidized food commodities to total food consumption is unknown. We estimated the proportion of individual energy intake from food commodities receiving the largest subsidies from 1995 to 2010 (corn, soyabeans, wheat, rice, sorghum, dairy and livestock). Integrating information from three federal databases (MyPyramid Equivalents, Food Intakes Converted to Retail Commodities, and What We Eat in America) with data from the 2001���2006 National Health and Nutrition Examination Surveys, we computed a Subsidy Score representing the percentage of total energy intake from subsidized commodities. We examined the score���s distribution and the probability of having a ���high��� (���70th percentile) v. ���low��� (���30th percentile) score, across the population and subgroups, using multivariate logistic regression. Community-dwelling adults in the USA. Participants (n 11 811) aged 18���64 years. Median Subsidy Score was 56��7 % (interquartile range 47��2���65��4 %). Young...
Women in the child-bearing age of 15 to 44 years and, in particular, pregnant and lactating women... more Women in the child-bearing age of 15 to 44 years and, in particular, pregnant and lactating women in this age cohort are considered a sensitive subpopulation when assessing risk from ingestion of water because water borne contaminants may pose a risk not only to the mother but to the fetus or infant. This article presents estimates of daily average per
The September 11, 2001 attack on the World Trade Center (WTC) covered a large area of downtown Ne... more The September 11, 2001 attack on the World Trade Center (WTC) covered a large area of downtown New York City with dust and debris. This paper describes the testing of an analytical method designed to evaluate whether sampled dust contains dust that may have originated from the collapse of the WTC. Using dust samples collected from locations affected and not affected (referred to as 'background' locations) by the collapse, a scanning electron microscopy (SEM) analysis method was developed to screen for three materials that are believed to be present in large quantities in WTC dusts: slag wool, concrete, and gypsum. An inter-laboratory evaluation of the method was implemented by having eight laboratories analyze a number of 'blind' dust samples, consisting of confirmed background dust and confirmed background dust spiked with varying amounts of dust affected by the WTC collapse. The levels of gypsum and concrete in the spiked samples were indistinguishable from the levels in the background samples. Measurements of slag wool in dust demonstrated potential for distinguishing between spiked and background samples in spite of considerable within and between laboratory variability. Slag wool measurements appear to be sufficiently sensitive to distinguish dust spiked with 5% WTC-affected dust from 22 out of 25 background dust samples. Additional development work and inter-laboratory testing of the slag wool component will be necessary to improve the precision and accuracy of the method and reduce inter- and intra-laboratory variability from levels observed in the inter-laboratory evaluation.
The use of analytical chemistry measurements in environmental monitoring is dependent on an asses... more The use of analytical chemistry measurements in environmental monitoring is dependent on an assessment of measurement error. This paper demonstrates the utility of a two-component error model in setting limits of detection and related concepts. The model is applicable to analytical methods in which high concentrations are measured with approximately constant relative standard deviation. At low levels, the relative standard deviation cannot stay constant, since this implies vanishingly small absolute standard deviation. The two-component model has approximately constant standard deviation near zero concentration, and approximately constant relative standard deviation at high concentrations, a pattern that is frequently observed in practice.
The contribution of subsidized food commodities to total food consumption is unknown. We estimate... more The contribution of subsidized food commodities to total food consumption is unknown. We estimated the proportion of individual energy intake from food commodities receiving the largest subsidies from 1995 to 2010 (corn, soyabeans, wheat, rice, sorghum, dairy and livestock). Integrating information from three federal databases (MyPyramid Equivalents, Food Intakes Converted to Retail Commodities, and What We Eat in America) with data from the 2001���2006 National Health and Nutrition Examination Surveys, we computed a Subsidy Score representing the percentage of total energy intake from subsidized commodities. We examined the score���s distribution and the probability of having a ���high��� (���70th percentile) v. ���low��� (���30th percentile) score, across the population and subgroups, using multivariate logistic regression. Community-dwelling adults in the USA. Participants (n 11 811) aged 18���64 years. Median Subsidy Score was 56��7 % (interquartile range 47��2���65��4 %). Young...
Women in the child-bearing age of 15 to 44 years and, in particular, pregnant and lactating women... more Women in the child-bearing age of 15 to 44 years and, in particular, pregnant and lactating women in this age cohort are considered a sensitive subpopulation when assessing risk from ingestion of water because water borne contaminants may pose a risk not only to the mother but to the fetus or infant. This article presents estimates of daily average per
The September 11, 2001 attack on the World Trade Center (WTC) covered a large area of downtown Ne... more The September 11, 2001 attack on the World Trade Center (WTC) covered a large area of downtown New York City with dust and debris. This paper describes the testing of an analytical method designed to evaluate whether sampled dust contains dust that may have originated from the collapse of the WTC. Using dust samples collected from locations affected and not affected (referred to as 'background' locations) by the collapse, a scanning electron microscopy (SEM) analysis method was developed to screen for three materials that are believed to be present in large quantities in WTC dusts: slag wool, concrete, and gypsum. An inter-laboratory evaluation of the method was implemented by having eight laboratories analyze a number of 'blind' dust samples, consisting of confirmed background dust and confirmed background dust spiked with varying amounts of dust affected by the WTC collapse. The levels of gypsum and concrete in the spiked samples were indistinguishable from the levels in the background samples. Measurements of slag wool in dust demonstrated potential for distinguishing between spiked and background samples in spite of considerable within and between laboratory variability. Slag wool measurements appear to be sufficiently sensitive to distinguish dust spiked with 5% WTC-affected dust from 22 out of 25 background dust samples. Additional development work and inter-laboratory testing of the slag wool component will be necessary to improve the precision and accuracy of the method and reduce inter- and intra-laboratory variability from levels observed in the inter-laboratory evaluation.
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