Henry D. Kahn

Evaluation of background exposures of Americans to dioxin-like compounds in the 1990s and the 2000s

The US Environmental Protection Agencys 2004 Dioxin Reassessment included a characterization of background exposures to dioxin-like compounds, including an estimate of an average background intake dose and an average background body burden. These quantities were derived from data generated in the mid-1990s. Studies conducted in the 2000s were gathered in an attempt to update the estimates generated by the Reassessment. While these studies suggest declines in the average background dose and body burden, a precise quantification of this decline, much less a conclusion that a decline has indeed occurred, cannot be made because of the inconsistency of study design and data sources, and the treatment of non-detects in the generation of congener average concentrations. The average background intake of the Reassessment was 61.0 pg TEQ/day, and using more current data, the average background intake was 40.6 pg TEQ/day. The average body burden from the surveys in the mid-1990s was 22.9 pg TEQ/g lipid weight (pg/g lwt). More recent blood concentration data, from NHANES 2001/2, suggest an adult average at 21.7 pg/g TEQ lwt. These TEQ values include the 17 dioxin and furan congeners and 3 coplanar PCBs, and were generated substituting ND=(1/2)DL or ND=DL/sq rt (2). Results are provided for ND=0 and analyses conducted to evaluate the impacts of this substitution. A more detailed examination of beef and pork data from similarly designed national statistical surveys show that declines in pork are statistically significant while the beef concentrations appeared to have remained constant between the time periods.

Estimated daily average per capita water ingestion by child and adult age categories based on USDA's 1994–1996 and 1998 continuing survey of food intakes by individuals

Water ingestion estimates are important for the assessment of risk to human populations of exposure to water-borne pollutants. This paper reports mean and percentile estimates of the distributions of daily average per capita water ingestion for a number of age range groups. The age ranges, based on guidance from the US EPAs Risk Assessment Forum, are narrow for younger ages when development is rapid and wider for older ages when the rate of development decreases. Estimates are based on data from the United States Department of Agricultures (USDAs) 1994–1996 and 1998 Continuing Survey of Food Intake by Individuals (CSFII). Water ingestion estimates include water ingested directly as a beverage and water added to foods and beverages during preparation at home or in local establishments. Water occurring naturally in foods or added by manufacturers to commercial products (beverage or food) is not included. Estimates are reported in milliliters (ml/person/day) and milliliters per kilogram of body weight (ml/kg/day). As a by-product of constructing estimates in terms of body weight of respondents, distributions of self-reported body weights based on the CSFII were estimated and are also reported here.

Modeling uncertainty in the measurement of low-level analytes in environmental analysis

The use of analytical chemistry measurements in environmental monitoring is dependent on an assessment of measurement error. Models for variation in measurements are needed to quantify uncertainty in measurements, set limits of detection, and preprocess data for more sophisticated analysis in prediction, classification, and clustering. This article explains how a two-component error model can be used to accomplish all of these objectives. In addition, we present applications to quantitating biomarkers of exposure to toxic substances using gene expression microarrays.

Use of statistical methods in industrial water pollution control regulations in the United States.

This paper describes the process for developing regulations limiting the discharge of pollutants from industrial sources into the waters of the United States. The process includies and surveys of the industry to define products, processes, wastewater sources and characteristics, appropriate subcategorization and control technologies in use. Limitations on the amounts of pollutants that may be discharged in treated wastewater are based on statistical analysis of physical and chemical analytical data characterizing the performance capability of technologies in use in the industry. A general discussion of the statistical approach employed is provided along with some examples based on work performed to support recently promulgated regulations. The determination of regulatory discharge limitations, based on estimates of percentiles of lognormal distributions of measured pollutant concentrations in treated wastewater, is presented. Modifications to account for different averaging periods and detection limit observations are discussed.

Estimates of Water Ingestion for Women in Pregnant, Lactating, and Non-Pregnant and Non-Lactating Child-Bearing Age Groups Based on USDA's 1994–96, 1998 Continuing Survey of Food Intake by Individuals

ABSTRACT 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 capita water ingestion for women of child-bearing age and in three subgroups: pregnant, lactating, and non-pregnant/non-lactating women. Estimates of means and upper percentiles of subgroup ingestion distributions were generated using participant responses and survey weights from the United States Department of Agricultures (USDA) 1994–96 and 1998 Continuing Survey of Food Intake by Individuals (CSFII). The ingestion estimates are empirical and not based on an assumed parametric distribution of daily average amount of water ingestion. Water occurring naturally in foods or added by manufacturers to commercial products is not included in the estimates presented. These estimates of water ingestion by women of child-bearing age are compared to those attributed to Ershow and Cantor (1989) by Burmaster (1998). These estimates, based on data collected in 1978, were used by Burmaster to characterize the distribution of daily average per capita ingestion as lognormal. The lognormal estimates of total water ingestion are generally greater than the total water ingestion estimates based on the CSFII data. Possible explanations for the differences are discussed.

Selection of Work Sampling Observation Times: Part II-Restricted Random Sampling

Abstract This paper considers the problem of sampling from a finite population defined on the interval (1, 2, …, T), using a restricted form of random sampling in which the spacing between consecutive observations must be at least some minimum value, M. For this type of restricted random sample, of size N, the value M can be arbitrarily specified in the range from zero, corresponding to simple random sampling with replacement, to a maximum of T/N, corresponding to systematic sampling. An efficient procedure is developed for generating a sample for specified values of N, M and T. It is then shown, by computer simulation, that values of M in the range from 60 to 90 percent of T/N retain most of the advantages of systematic sampling, while avoiding most of the disadvantages for some special processes., Also, the error variance associated with stratified sampling is comparable to restricted random sampling with a minimum spacing of about 70 percent, and both methods are almost as efficient as systematic sampling.

Comment on: "Summary of the development of a signature for the detection of residual dust from collapse of the World Trade Center buildings".

Comment on: “Summary of the development of a signature for the detection of residual dust from collapse of the World Trade Center buildings”

Estimates of Water Ingestion in Formula by Infants and Children Based on USDA's 1994–1996 and 1998 Continuing Survey of Food Intakes by Individuals

ABSTRACT Assessment of risk to infants and children resulting from the ingestion of contaminants in water is an important component of the analysis of possible environmental hazards. Children and infants represent a sensitive life stage because exposure to contaminants in early life can have developmental and long-lasting adverse effects. Children and infants tend to ingest relatively large amounts of water on a bodyweight-adjusted basis, especially those that are fed in early life with formula that is re-constituted or diluted with water. This article presents statistical estimates of the amounts of community water ingested by formula-fed infants based on nationwide sample survey data that support identification of respondents who consume formula and the amounts of water they ingest. Included are specific estimates of the amounts of community water ingested in formula. Estimates of total community water ingestion by children and infants who consume formula can be especially useful in exposure assessment since they represent a highly exposed population. For example, mean community water ingestion by infants 1 to 3 months of age who consume formula is 627 mL/day (136 mL/kg/day) and the 95th percentile is 1096 mL/day (290 mL/kg/day).

Statistical evaluation of data from multi-laboratory testing of a measurement method intended to indicate the presence of dust resulting from the collapse of the World Trade Center

In this paper we describe a statistical analysis of the inter-laboratory data summarized in Rosati et al. (2008) to assess the performance of an analytical method to detect the presence of dust from the collapse of the World Trade Center (WTC) on September 11, 2001. The focus of the inter-lab study was the measurement of the concentration of slag wool fibers in dust which was considered to be an indicator of WTC dust. Eight labs were provided with two blinded samples each of three batches of dust that varied in slag wool concentration. Analysis of the data revealed that three of labs, which did not meet measurement quality objectives set forth prior to the experimental work, were statistically distinguishable from the five labs that did meet the quality objectives. The five labs, as a group, demonstrated better measurement capability although their ability to distinguish between the batches was somewhat mixed. This work provides important insights for the planning and implementation of future studies involving examination of dust samples for physical contaminants. This work demonstrates (a) the importance of controlling the amount of dust analyzed, (b) the need to take additional replicates to improve count estimates, and (c) the need to address issues related to the execution of the analytical methodology to ensure all labs meet the measurement quality objectives.