K. Udeni Alwis

Simultaneous analysis of 28 urinary VOC metabolites using ultra high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI/MSMS) ☆

Volatile organic compounds (VOCs) are ubiquitous in the environment, originating from many different natural and anthropogenic sources, including tobacco smoke. Long-term exposure to certain VOCs may increase the risk for cancer, birth defects, and neurocognitive impairment. Therefore, VOC exposure is an area of significant public health concern. Urinary VOC metabolites are useful biomarkers for assessing VOC exposure because of non-invasiveness of sampling and longer physiological half-lives of urinary metabolites compared with VOCs in blood and breath. We developed a method using reversed-phase ultra high performance liquid chromatography (UPLC) coupled with electrospray ionization tandem mass spectrometry (ESI/MSMS) to simultaneously quantify 28 urinary VOC metabolites as biomarkers of exposure. We describe a method that monitors metabolites of acrolein, acrylamide, acrylonitrile, benzene, 1-bromopropane, 1,3-butadiene, carbon-disulfide, crotonaldehyde, cyanide, N,N-dimethylformamide, ethylbenzene, ethylene oxide, propylene oxide, styrene, tetrachloroethylene, toluene, trichloroethylene, vinyl chloride and xylene. The method is accurate (mean accuracy for spiked matrix ranged from 84 to 104%), sensitive (limit of detection ranged from 0.5 to 20 ng mL(-1)) and precise (the relative standard deviations ranged from 2.5 to 11%). We applied this method to urine samples collected from 1203 non-smokers and 347 smokers and demonstrated that smokers have significantly elevated levels of tobacco-related biomarkers compared to non-smokers. We found significant (p<0.0001) correlations between serum cotinine and most of the tobacco-related biomarkers measured. These findings confirm that this method can effectively quantify urinary VOC metabolites in a population exposed to volatile organics.

Perchlorate, Nitrate, and Iodide Intake through Tap Water

Perchlorate is ubiquitous in the environment, leading to human exposure and potential impact on thyroid function. Nitrate can also competitively inhibit iodide uptake at the sodium-iodide symporter and thus reduce thyroid hormone production. This study investigates the intake of perchlorate, nitrate, and iodide attributable to direct and indirect tap water consumption. The National Health and Nutrition Examination Survey collected tap water samples and consumption data from 3262 U.S. residents during the years 2005-2006. The median perchlorate, nitrate, and iodide levels measured in tap water were 1.16, 758, and 4.55 μg/L, respectively. Measured perchlorate levels were below the United States Environmental Protection Agency (U.S. EPA) drinking water equivalent level for perchlorate (24.5 μg/L). Significant correlations were found between iodide and nitrate levels (r = 0.17, p < 0.0001) and perchlorate and nitrate levels (r = 0.25, p < 0.0001). On the basis of 24 h recall, 47% of the study participants reported drinking tap water; 89% reported either direct or indirect consumption of tap water. For the adult population (age ≥ 20 yrs) the median tap water consumption rate was 11.6 mL/kg-day. Using individual tap water consumption data and body weight, we estimated the median perchlorate, nitrate, and iodide dose attributable to tap water as 9.11, 11300, and 43.3 ng/kg-day, respectively, for U.S. adults. This perchlorate exposure dose from tap water is relatively small compared to the total perchlorate exposure dose previously characterized for the U.S. adults (median 64 ng/kg-day) and the U.S. EPA reference dose (700 ng/kg-day).

Urinary perchlorate as a measure of dietary and drinking water exposure in a representative sample of the United States population 2001-2008.

Perchlorate (ClO4−) is ubiquitous in the environment and inhibits the thyroid’s uptake of iodide. Food and tap water are likely sources of environmental exposure to perchlorate. The aim of this study was to identify significant dietary sources of perchlorate using perchlorate measured in urine as an exposure indicator. Sample-weighted, age-stratified linear regression models of National Health and Nutrition Examination Survey (NHANES) 2001–2008 data (n=16,955 participants) characterized the association between urinary perchlorate and the mass consumed in USDA food groups, controlling for urinary creatinine and other potential confounders. Separate models of NHANES 2005–2006 data (n=2841) evaluated the association between urinary perchlorate and perchlorate consumed via residential tap water. Consumption of milk products was associated with statistically significant contributions to urinary perchlorate across all age strata: 2.93 ng ClO4−/ml per kg consumed for children (6–11 years-old (YO)); 1.54 ng ClO4−/ml per kg for adolescents (12–19 YO); and 0.69 ng ClO4−/ml per kg for adults (20–84 YO). Vegetables were a significant contributor for adolescents and adults, whereas fruits and eggs contributed significantly only for adults. Dark-green leafy vegetables contributed the most among all age strata: 30.83 ng ClO4−/ml per kg for adults. Fats, oils, and salad dressings were significant contributors only for children. Three food groups were negatively associated with urinary perchlorate: grain products for children; sugars, sweets, and beverages for adolescents; and home tap water for adults. In a separate model, however, perchlorate consumed via home tap water contributed significantly to adult urinary perchlorate: 2.11E–4 ng ClO4−/ml per ng perchlorate in tap water consumed. In a nationally representative sample of the United States 6–84 YO, diet and tap water contributed significantly to urinary perchlorate, with diet contributing substantially more than tap water.

Perchlorate, nitrate, thiocyanate, and iodide levels in chicken feed, water, and eggs from three farms.

Perchlorate is an inhibitor of iodide uptake that is found widely in the environment. Given the potential for perchlorate accumulation during egg formation and the widespread consumption of eggs, it is important to examine eggs as a source of exposure to perchlorate and other potential inhibitors of iodide uptake (nitrate and thiocyanate). This study was conducted to determine potential human exposure to perchlorate from eggs produced by chicken flocks consuming differing amounts of perchlorate. The mean concentrations of perchlorate (7.16 ( 1.99 microg/kg of dry weight), nitrate (2820 ( 2100 microg/kg of dry weight), thiocyanate (574 +/- 433 microg/kg of dry weight), and iodide (2980 ( 1490 microg/kg of dry weight) in eggs (n = 180) from 15 chicken houses on 3 U.S. farms were determined. Chickens secreted into eggs an average of 23% of the perchlorate ingested from feed and water. Perchlorate levels in eggs were positively correlated with perchlorate intake (p < 0.001). Increased intake of perchlorate, nitrate, and thiocyanate was associated with decreased iodide levels in eggs, possibly indicating a competitive transport mechanism, such as sodium-iodide symporter. It was estimated that egg consumption contributes minimal perchlorate (approximately 0.040 microg) compared to the average total intake of approximately 10.5 microg for U.S. adults. Additionally, it was found that egg consumption was not associated with increased perchlorate exposure in 2820 individuals from the National Health and Nutrition Examination Survey (p value for the difference of least-squares means, pDiff = 0.225). From these findings it was concluded that, although chickens secrete perchlorate in eggs, eggs do not appear to be a significant source of perchlorate exposure for adults in the United States.

Acrolein Exposure in U.S. Tobacco Smokers and Non-Tobacco Users: NHANES 2005–2006

Background Acrolein is a highly reactive α,β unsaturated aldehyde and respiratory irritant. Acrolein is formed during combustion (e.g., burning tobacco or biomass), during high-temperature cooking of foods, and in vivo as a product of oxidative stress and polyamine metabolism. No biomonitoring reference data have been reported to characterize acrolein exposure for the U.S. population. Objectives Our goals were to a) evaluate two acrolein metabolites in urine—N-acetyl-S-(3-hydroxypropyl)-l-cysteine (3HPMA) and N-acetyl-S-(2-carboxyethyl)-l-cysteine (CEMA)—as biomarkers of exposure to acrolein for the U.S. population by age, sex, race, and smoking status; and b) assess tobacco smoke as a predictor of acrolein exposure. Methods We analyzed urine from National Health and Nutrition Examination Survey (NHANES 2005–2006) participants ≥ 12 years old (n = 2,866) for 3HPMA and CEMA using ultra-high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC/ESI-MSMS). Sample-weighted linear regression models stratified for non-tobacco users versus tobacco smokers (as defined by serum cotinine and self-report) characterized the association of urinary 3HPMA and CEMA with tobacco smoke exposure, adjusting for urinary creatinine, sex, age, and race/ethnicity. Results 3HPMA and CEMA levels were higher among tobacco smokers (cigarettes, cigars, and pipe users) than among non-tobacco users. The median 3HPMA levels for tobacco smokers and non-tobacco users were 1,089 and 219 μg/g creatinine, respectively. Similarly, median CEMA levels were 203 μg/g creatinine for tobacco smokers and 78.8 μg/g creatinine for non-tobacco users. Regression analysis showed that serum cotinine was a significant positive predictor (p < 0.0001) of both 3HPMA and CEMA among tobacco smokers. Conclusions Tobacco smoke was a significant predictor of acrolein exposure in the U.S. population. Citation Alwis KU, deCastro BR, Morrow JC, Blount BC. 2015. Acrolein exposure in U.S. tobacco smokers and non-tobacco users: NHANES 2005–2006. Environ Health Perspect 123:1302–1308; http://dx.doi.org/10.1289/ehp.1409251

Development of urine standard reference materials for metabolites of organic chemicals including polycyclic aromatic hydrocarbons, phthalates, phenols, parabens, and volatile organic compounds

AbstractTwo new Standard Reference Materials (SRMs), SRM 3672 Organic Contaminants in Smokers’ Urine (Frozen) and SRM 3673 Organic Contaminants in Non-Smokers’ Urine (Frozen), have been developed in support of studies for assessment of human exposure to select organic environmental contaminants. Collaborations among three organizations resulted in certified values for 11 hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) and reference values for 11 phthalate metabolites, 8 environmental phenols and parabens, and 24 volatile organic compound (VOC) metabolites. Reference values are also available for creatinine and the free forms of caffeine, theobromine, ibuprofen, nicotine, cotinine, and 3-hydroxycotinine. These are the first urine Certified Reference Materials characterized for metabolites of organic environmental contaminants. Noteworthy, the mass fractions of the environmental organic contaminants in the two SRMs are within the ranges reported in population survey studies such as the National Health and Nutrition Examination Survey (NHANES) and the Canadian Health Measures Survey (CHMS). These SRMs will be useful as quality control samples for ensuring compatibility of results among population survey studies and will fill a void to assess the accuracy of analytical methods used in studies monitoring human exposure to these organic environmental contaminants. Graphical AbstractMetabolites of PAHs, Phthalates, Phenols, Parabens, and VOCs in Urine SRMs

Urinary concentrations of PAH and VOC metabolites in marijuana users

BACKGROUND Marijuana is seeing increased therapeutic use, and is the worlds third most-popular recreational drug following alcohol and tobacco. This widening use poses increased exposure to potentially toxic combustion by-products from marijuana smoke and the potential for public health concerns. OBJECTIVES To compare urinary metabolites of polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) among self-reported recent marijuana users and nonusers, while accounting for tobacco smoke exposure. METHODS Measurements of PAH and VOC metabolites in urine samples were combined with questionnaire data collected from participants in the National Health and Nutrition Examination Surveys (NHANES) from 2005 to 2012 in order to categorize participants (≥18years) into exclusive recent marijuana users and nonusers. Adjusted geometric means (GMs) of urinary concentrations were computed for these groups using multiple regression analyses to adjust for potential confounders. RESULTS Adjusted GMs of many individual monohydroxy PAHs (OH-PAHs) were significantly higher in recent marijuana users than in nonusers (p<0.05). Urinary thiocyanate (p<0.001) and urinary concentrations of many VOC metabolites, including metabolites of acrylonitrile (p<0.001) and acrylamide (p<0.001), were significantly higher in recent marijuana users than in nonusers. CONCLUSIONS We found elevated levels of biomarkers for potentially harmful chemicals among self-identified, recent marijuana users compared with nonusers. These findings suggest that further studies are needed to evaluate the potential health risks to humans from the exposure to these agents when smoking marijuana.

Styrene‐associated health outcomes at a windblade manufacturing plant

BACKGROUND Health risks of using styrene to manufacture windblades for the green energy sector are unknown. METHODS Using data collected from 355 (73%) current windblade workers and regression analysis, we investigated associations between health outcomes and styrene exposure estimates derived from urinary styrene metabolites. RESULTS The median current styrene exposure was 53.6 mg/g creatinine (interquartile range: 19.5-94.4). Color blindness in men and women (standardized morbidity ratios 2.3 and 16.6, respectively) was not associated with exposure estimates, but was the type previously reported with styrene. Visual contrast sensitivity decreased and chest tightness increased (odds ratio 2.9) with increasing current exposure. Decreases in spirometric parameters and FeNO, and increases in the odds of wheeze and asthma-like symptoms (odds ratios 1.3 and 1.2, respectively) occurred with increasing cumulative exposure. CONCLUSIONS Despite styrene exposures below the recommended 400 mg/g creatinine, visual and respiratory effects indicate the need for additional preventative measures in this industry.