Ben Blount

Design and methods of the Population Assessment of Tobacco and Health (PATH) Study

Background This paper describes the methods and conceptual framework for Wave 1 of the Population Assessment of Tobacco and Health (PATH) Study data collection. The National Institutes of Health, through the National Institute on Drug Abuse, is partnering with the Food and Drug Administrations (FDA) Center for Tobacco Products to conduct the PATH Study under a contract with Westat. Methods The PATH Study is a nationally representative, longitudinal cohort study of 45 971 adults and youth in the USA, aged 12 years and older. Wave 1 was conducted from 12 September 2013 to 15 December 2014 using Audio Computer-Assisted Self-Interviewing to collect information on tobacco-use patterns, risk perceptions and attitudes towards current and newly emerging tobacco products, tobacco initiation, cessation, relapse behaviours and health outcomes. The PATH Studys design allows for the longitudinal assessment of patterns of use of a spectrum of tobacco products, including initiation, cessation, relapse and transitions between products, as well as factors associated with use patterns. Additionally, the PATH Study collects biospecimens from consenting adults aged 18 years and older and measures biomarkers of exposure and potential harm related to tobacco use. Conclusions The cumulative, population-based data generated over time by the PATH Study will contribute to the evidence base to inform FDAs regulatory mission under the Family Smoking Prevention and Tobacco Control Act and efforts to reduce the Nations burden of tobacco-related death and disease.

Temporal variability in urinary concentrations of perchlorate, nitrate, thiocyanate and iodide among children.

Perchlorate, nitrate and thiocyanate are ubiquitous in the environment, and human exposure to these chemicals is accurately measured in urine. Biomarkers of these chemicals represent a persons recent exposure, however, little is known on the temporal variability of the use of a single measurement of these biomarkers. Healthy Hispanic and Black children (6–10-year-old) donated urine samples over 6 months. To assess temporal variability, we used three statistical methods (n=29; 153 urine samples): intraclass correlation coefficient (ICC), Spearmans correlation coefficient between concentrations measured at different timepoints and surrogate category analysis to assess how well tertile ranking by a single biomarker measurement represented the average concentration over 6 months. The ICC measure of reproducibility was poor (0.10–0.12) for perchlorate, nitrate and iodide; and fair for thiocyanate (0.36). The correlations for each biomarker across multiple sampling times ranged from 0.01–0.57. Surrogate analysis showed consistent results for almost every surrogate tertile. Results demonstrate fair temporal reliability in the spot urine concentrations of the three NIS inhibitors and iodide. Surrogate analysis show that single-spot urine samples reliably categorize participants exposure providing support for the use of a single sample as an exposure measure in epidemiological studies that use relative ranking of exposure.

Chemical-specific screening criteria for interpretation of biomonitoring data for volatile organic compounds (VOCs) - application of steady-state PBPK model solutions

The National Health and Nutrition Examination Survey (NHANES) generates population-representative biomonitoring data for many chemicals including volatile organic compounds (VOCs) in blood. However, no health or risk-based screening values are available to evaluate these data from a health safety perspective or to use in prioritizing among chemicals for possible risk management actions. We gathered existing risk assessment-based chronic exposure reference values such as reference doses (RfDs), reference concentrations (RfCs), tolerable daily intakes (TDIs), cancer slope factors, etc. and key pharmacokinetic model parameters for 47 VOCs. Using steady-state solutions to a generic physiologically-based pharmacokinetic (PBPK) model structure, we estimated chemical-specific steady-state venous blood concentrations across chemicals associated with unit oral and inhalation exposure rates and with chronic exposure at the identified exposure reference values. The geometric means of the slopes relating modeled steady-state blood concentrations to steady-state exposure to a unit oral dose or unit inhalation concentration among 38 compounds with available pharmacokinetic parameters were 12.0 microg/L per mg/kg-d (geometric standard deviation [GSD] of 3.2) and 3.2 microg/L per mg/m(3) (GSD=1.7), respectively. Chemical-specific blood concentration screening values based on non-cancer reference values for both oral and inhalation exposure range from 0.0005 to 100 microg/L; blood concentrations associated with cancer risk-specific doses at the 1E-05 risk level ranged from 5E-06 to 6E-02 microg/L. The distribution of modeled steady-state blood concentrations associated with unit exposure levels across VOCs may provide a basis for estimating blood concentration screening values for VOCs that lack chemical-specific pharmacokinetic data. The screening blood concentrations presented here provide a tool for risk assessment-based evaluation of population biomonitoring data for VOCs and are most appropriately applied to central tendency estimates for such datasets.

The Effects of Perchlorate on Thyroidal Gene Expression are Different from the Effects of Iodide Deficiency

Perchlorate (ClO4 −), which is a ubiquitous and persistent ion, competitively interferes with iodide (I) accumulation in the thyroid, producing I deficiency (ID), which may result in reduced thyroid hormone synthesis and secretion. Human studies suggest that ClO4 − presents little risk in healthy individuals; however, the precautionary principle demands that the sensitive populations of ID adults and mothers require extra consideration. In an attempt to determine whether the effects on gene expression were similar, the thyroidal effects of ClO4 − (10 mg/kg) treatment for 14 d in drinking water were compared with those produced by 8 wk of ID in rats. The thyroids were collected (n = 3 each group) and total mRNA was analyzed using the Affymetrix Rat Genome 230 2.0 GeneChip. Changes in gene expression were compared with appropriate control groups. The twofold gene changes due to ID were compared with alterations due to ClO4 − treatment. One hundred and eighty-nine transcripts were changed by the ID diet and 722 transcripts were altered by the ClO4 − treatment. Thirty-four percent of the transcripts changed by the I-deficient diet were also altered by ClO4 − and generally in the same direction. Three specific transporter genes, AQP1, NIS, and SLC22A3, were changed by both treatments, indicating that the membrane-specific changes were similar. Iodide deficiency primarily produced alterations in retinol and calcium signaling pathways and ClO4 − primarily produced changes related to the accumulation of extracellular matrix proteins. This study provides evidence that ClO4 −, at least at this dose level, changes more genes and alters different genes compared to ID.

Evaluation of NHANES biomonitoring data for volatile organic chemicals in blood: Application of chemical-specific screening criteria

Available biomonitoring data for volatile organic chemicals (VOCs) in blood from the National Health and Nutrition Examination Survey (NHANES) (2003–2004) (CDC, 2009) were compared with recently derived screening biomonitoring equivalent (BE) values (Aylward et al., 2010). A BE is defined as the estimated concentration or range of concentrations of a chemical or its metabolites in a biological medium (blood, urine, or other medium) that is consistent with an existing health-based exposure guidance value. Blood concentrations of VOCs from the NHANES data set were compared with predicted screening BE values based upon a hazard quotient (HQ) for individual chemicals, and a hazard index (HI) approach for combined exposures. HI values for detected chemicals were generally at or below a value of 1, suggesting that the potential for deleterious effects is low. However, smoking was an important determinant of HI and HQ values. Detected levels of benzene in non-smokers were within the range of BE values corresponding to a 1 × 10−6–1 × 10−4 range for upper-bound cancer risk; in smokers, levels of benzene were at the upper end of or exceeded this range. For VOCs that were not detected in the NHANES sampling, analytical detection limits were generally sufficiently sensitive to detect concentrations consistent with existing non-cancer and cancer risk-based exposure guidance values. Interpretations of measured blood concentrations of VOCs must be made with caution due to the substantial within-individual, within-day fluctuations in levels expected due to the rapid elimination of VOCs.

Iodine status in Turkish populations and exposure to iodide uptake inhibitors.

Perchlorate, nitrate, and thiocyanate are competitive inhibitors of the sodium iodide symporter of the thyroid membrane. These inhibitors can decrease iodine uptake by the symporter into the thyroid gland and may disrupt thyroid function. This study assesses iodine status and exposure to iodide uptake inhibitors of non-pregnant and non-lactating adult women living in three different cities in Turkey (Istanbul, Isparta and Kayseri). We measured iodine and iodide uptake inhibitors in 24-hr urines collected from study participants (N = 255). All three study populations were mildly iodine deficient, with median urinary iodine (UI) levels of 77.5 µg/L in Istanbul, 58.8 µg/L in Isparta, and 69.8 µg/L in Kayseri. Perchlorate doses were higher in the study population (median 0.13 µg/kg/day), compared with a reference population (median 0.059 µg/kg/day), but lower than the U.S. EPA reference dose (0.7 µg/kg/day). Urinary thiocyanate levels increased with increasing exposure to tobacco smoke, with non-smokers (268 µg/L) significantly lower than light smokers (1110 µg/L), who were significantly lower than heavy smokers (2410 µg/L). This pilot study provides novel data indicating that study participants were moderately iodine deficient and had higher intakes of the iodide uptake inhibitor perchlorate compared with a reference population. Further investigation is needed to characterize the thyroid impact resulting from iodine deficiency coupled with exposure to iodide uptake inhibitors such as perchlorate, thiocyanate and nitrate.

Neurologic Manifestations Associated with an Outbreak of Typhoid Fever, Malawi - Mozambique, 2009: An Epidemiologic Investigation

Background The bacterium Salmonella enterica serovar Typhi causes typhoid fever, which is typically associated with fever and abdominal pain. An outbreak of typhoid fever in Malawi-Mozambique in 2009 was notable for a high proportion of neurologic illness. Objective Describe neurologic features complicating typhoid fever during an outbreak in Malawi-Mozambique Methods Persons meeting a clinical case definition were identified through surveillance, with laboratory confirmation of typhoid by antibody testing or blood/stool culture. We gathered demographic and clinical information, examined patients, and evaluated a subset of patients 11 months after onset. A sample of persons with and without neurologic signs was tested for vitamin B6 and B12 levels and urinary thiocyanate. Results Between March – November 2009, 303 cases of typhoid fever were identified. Forty (13%) persons had objective neurologic findings, including 14 confirmed by culture/serology; 27 (68%) were hospitalized, and 5 (13%) died. Seventeen (43%) had a constellation of upper motor neuron findings, including hyperreflexia, spasticity, or sustained ankle clonus. Other neurologic features included ataxia (22, 55%), parkinsonism (8, 20%), and tremors (4, 10%). Brain MRI of 3 (ages 5, 7, and 18 years) demonstrated cerebral atrophy but no other abnormalities. Of 13 patients re-evaluated 11 months later, 11 recovered completely, and 2 had persistent hyperreflexia and ataxia. Vitamin B6 levels were markedly low in typhoid fever patients both with and without neurologic signs. Conclusions Neurologic signs may complicate typhoid fever, and the diagnosis should be considered in persons with acute febrile neurologic illness in endemic areas.

Direct Measurement of Perchlorate Exposure Biomarkers in a Highly Exposed Population: A Pilot Study

Exposure to perchlorate is ubiquitous in the United States and has been found to be widespread in food and drinking water. People living in the lower Colorado River region may have perchlorate exposure because of perchlorate in ground water and locally-grown produce. Relatively high doses of perchlorate can inhibit iodine uptake and impair thyroid function, and thus could impair neurological development in utero. We examined human exposures to perchlorate in the Imperial Valley among individuals consuming locally grown produce and compared perchlorate exposure doses to state and federal reference doses. We collected 24-hour urine specimen from a convenience sample of 31 individuals and measured urinary excretion rates of perchlorate, thiocyanate, nitrate, and iodide. In addition, drinking water and local produce were also sampled for perchlorate. All but two of the water samples tested negative for perchlorate. Perchlorate levels in 79 produce samples ranged from non-detect to 1816 ppb. Estimated perchlorate doses ranged from 0.02 to 0.51 µg/kg of body weight/day. Perchlorate dose increased with the number of servings of dairy products consumed and with estimated perchlorate levels in produce consumed. The geometric mean perchlorate dose was 70% higher than for the NHANES reference population. Our sample of 31 Imperial Valley residents had higher perchlorate dose levels compared with national reference ranges. Although none of our exposure estimates exceeded the U. S. EPA reference dose, three participants exceeded the acceptable daily dose as defined by bench mark dose methods used by the California Office of Environmental Health Hazard Assessment.

Exposure to Perchlorate in Lactating Women and Its Associations With Newborn Thyroid Stimulating Hormone

Background: Perchlorate, thiocyanate, and nitrate can block iodide transport at the sodium iodide symporter (NIS) and this can subsequently lead to decreased thyroid hormone production and hypothyroidism. NIS inhibitor exposure has been shown to reduce iodide uptake and thyroid hormone levels; therefore we hypothesized that maternal NIS inhibitor exposure will influence both maternal and newborn thyroid function. Methods: Spot urine samples were collected from 185 lactating mothers and evaluated for perchlorate, thiocyanate, and nitrate concentrations. Blood and colostrum samples were collected from the same participants in the first 48 h after delivery. Thyroid hormones and thyroid-related antibodies (TSH, fT3, fT4, anti-TPO, anti-Tg) were analyzed in maternal blood and perchlorate was analyzed in colostrum. Also, spot blood samples were collected from newborns (n = 185) between 48 and 72 postpartum hours for TSH measurement. Correlation analysis was performed to assess the effect of NIS inhibitors on thyroid hormone levels of lactating mothers and their newborns in their first 48 postpartum hours. Results: The medians of maternal urinary perchlorate (4.00 μg/g creatinine), maternal urinary thiocyanate (403 μg/g creatinine), and maternal urinary nitrate (49,117 μg/g creatinine) were determined. Higher concentrations of all three urinary NIS inhibitors (μg/g creatinine) at their 75th percentile levels were significantly correlated with newborn TSH (r = 0.21, p < 0.001). Median colostrum perchlorate level concentration of all 185 participants was 2.30 μg/L. Colostrum perchlorate was not significantly correlated with newborn TSH (p > 0.05); however, there was a significant correlation between colostrum perchlorate level and maternal TSH (r = 0.21, p < 0.01). Similarly, there was a significant positive association between colostrum perchlorate and maternal urinary creatinine adjusted perchlorate (r = 0.32, p < 0.001). Conclusion: NIS inhibitors are ubiquitous in lactating women in Turkey and are associated with increased TSH levels in newborns, thus signifying for the first time that co-exposure to maternal NIS inhibitors can have a negative effect on the newborn thyroid function.