Assessment of human hair as an indicator of exposure to organophosphate flame retardants. Case study on a Norwegian mother–child cohort

A major challenge of non-invasive human biomonitoring using hair is to assess whether it can be used as an indicator of exposure to Flame Retardants, such as Organophosphate Flame Retardants (PFRs), since the contribution of atmospheric deposition (air and/or dust) cannot be neglected. Therefore, the aim of this study was to evaluate the suitability of using human hair more thoroughly by comparison of (i) levels of PFRs in human hair (from 48 mothers and 54 children), with levels measured in dust and air in their respective households; and (ii) levels of selected PFRs in hair with the levels of corresponding PFR metabolites in matching urine samples collected simultaneously. Most PFRs (tri-n-butyl phosphate (TNBP), 2-ethyl-hexyldiphenyl phosphate (EHDPHP), tri-phenyl phosphate (TPHP), tri-iso-butyl phosphate (TIBP), and tris(2-butoxyethyl) phosphate (TBOEP)) were detected in all human hair samples, tris(2-ethylhexyl) phosphate (TEHP) and tris(1,3-dichloro-iso-propyl) phosphate (TDCIPP) in 93%, tri-cresyl-phosphate (TCP) in 69% and tris(2-chloroethyl) phosphate (TCEP) in 21% of the samples. Levels of individual PFRs ranged between < 1 and 3744 ng/g hair and were lower than in indoor dust from the participants' homes. Several statistically significant associations between PFR levels in human hair and PFR levels in house dust and/or air were found, e.g. Spearman correlation (r_S = 0.561, p < 0.05) between TBOEP in children's hair and in indoor air. Also, associations were found between TDCIPP in hair and its metabolite bis(1,3-dichloro-iso-propyl) phosphate (BDCIPP) in urine; they were stronger for children (e.g. Pearson correlation r_P = 0.475; p = 0.001) than for mothers (r_P = 0.395, p = 0.01). Levels of diphenyl phosphate (DPHP) in mothers' and children's urine were slightly correlated (r_S = 0.409, p = 0.008), suggesting similar sources of exposure. To the best of our knowledge, this is the first study with such design and our findings might help to understand human exposure to and body burdens of PFRs.     

Multimycotoxin analysis in urines to assess infant exposure: A case study in Cameroon

This study was conducted to investigate mycotoxin exposure in children (n = 220, aged 1.5–4.5 years) from high mycotoxin contamination regions of Cameroon and to examine the association between the mycotoxin levels (in total 18 analytes) and several socio-demographic factors and anthropometric characteristics. A cross-sectional study was conducted in six villages in Cameroon with 220 children. Mycotoxins and their metabolites were detected in 160/220 (73%) urine samples.There were significant differences in the mean contamination levels of ochratoxin A (p = 0.01) and β-zearalenol (p = 0.017) between the two agro-ecological zones investigated. Likewise significant differences were observed in the mean levels of aflatoxin M₁ (p = 0.001) across the weaning categories of these children. The mean concentration of aflatoxin M₁ detected in the urine of the partially breastfed children (1.43 ng/mL) was significantly higher (p = 0.001) than those of the fully weaned children (0.282 ng/mL).Meanwhile, the mean concentrations of deoxynivalenol (3.0 ng/mL) and fumonisin B₁ (0.59 ng/mL) detected in the urine of the male children was significantly (p value 0.021 for deoxynivalenol and 0.004 for fumonisin B₁) different from the levels detected in the urine of female children; 0.71 ng/mL and 0.01 ng/mL for deoxynivalenol and fumonisin B₁ respectively. In this study, there was no association between the different malnutrition categories (stunted, wasting and underweight) and the mycotoxin concentrations detected in the urine of these children.However, there is sufficient evidence to suggest that children in Cameroon under the age 5 are exposed to high levels of carcinogenic substances such as fumonisin B₁, aflatoxin M₁ and ochratoxin A through breastfeeding. To the best of our knowledge, this is the first report of its kind carried out in West Africa to determine multi-mycotoxin exposure in infants.     

Predictors of exposure to organophosphate pesticides in schoolchildren in the Province of Talca,Chile

BackgroundFew data exist in Latin America concerning the association between organophosphate (OP) urinary metabolites and the consumption of fruits and vegetables and other exposure risk variables in schoolchildren.MethodsWe collected samples of urine from 190 Chilean children aged 6–12 years, fruits and vegetables, water and soil from schools and homes, and sociodemographic data through a questionnaire. We measured urinary dialkylphosphate (DAP) OP metabolites and OP pesticide residues in food consumed by these 190 children during two seasons: December 2010 (summer) and May 2011 (fall). We analyzed the relationship between urinary DAP concentrations and pesticide residues in food, home pesticide use, and residential location.ResultsDiethylalkylphosphates (DEAP) and dimethylalkylphosphates (DMAP) were detected in urine in 76% and 27% of the samples, respectively. Factors associated with urinary DEAP included chlorpyrifos in consumed fruits (p < 0.0001), urinary creatinine (p < 0.0001), rural residence (p = 0.02) and age less than 9 years (p = 0.004). Factors associated with urinary DMAP included the presence of phosmet residues in fruits (p < 0.0001), close proximity to a farm (p = 0.002), home fenitrothion use (p = 0.009), and season (p < 0.0001).ConclusionsUrinary DAP levels in Chilean school children were high compared to previously reported studies. The presence of chlorpyrifos and phosmet residues in fruits was the major factor predicting urinary DAP metabolite concentrations in children.     

Measuring environmental stress in East Greenland polar bears, 1892–1927 and 1988–2009: What does hair cortisol tell us?

Hair sampled from 96 East Greenland polar bears (Ursus maritimus) over the periods 1892–1927 and 1988–2009 was analyzed for cortisol as a proxy to investigate temporal patterns of environmental stress. Cortisol concentration was independent of sex and age, and was found at significantly higher (p < 0.001) concentrations in historical hair samples (1892–1927; n = 8) relative to recent ones (1988–2009; n = 88). In addition, there was a linear time trend in cortisol concentration of the recent samples (p < 0.01), with an annual decrease of 2.7%. The recent hair samples were also analyzed for major bioaccumulative, persistent organic pollutants (POPs). There were no obvious POP related time trends or correlations between hair cortisol and hair POP concentrations. Thus, polar bear hair appears to be a relatively poor indicator of the animal's general POP load in adipose tissue. However, further investigations are warranted to explore the reasons for the temporal decrease found in the bears' hair cortisol levels.     

Respiratory medication sales and urban air pollution in Brussels (2005 to 2011)

BackgroundWe investigated the associations between daily sales of respiratory medication and air pollutants in the Brussels-Capital Region between 2005 and 2011.MethodsWe used over-dispersed Poisson Generalized Linear Models to regress daily individual reimbursement data of prescribed asthma and COPD medication from the social security database against each subject's residential exposure to outdoor particulate matter (PM₁₀) or NO₂ estimated, by interpolation from monitoring stations. We calculated cumulative risk ratios (RR) and their 95% confidence intervals (CI) for interquartile ranges (IQR) of exposure for different windows of past exposure for the entire population and for seven age groups.ResultsMedian daily concentrations of PM₁₀ and NO₂ were 25 μg/m³ (IQR = 17.1) and 38 μg/m³ (IQR = 20.5), respectively. PM₁₀ was associated with daily medication sales among individuals aged 13 to 64 y. For NO₂, significant associations were observed among all age groups except > 84 y. The highest RR were observed for NO₂, among adolescents, including three weeks lags (RR = 1.187 95%CI: 1.097–1.285).ConclusionThe associations found between temporal changes in exposure to air pollutants and daily sales of respiratory medication in Brussels indicate that urban air pollution contributes to asthma and COPD morbidity in the general population.     

Daily intake of bisphenol A and triclosan and their association with anthropometric data,thyroid hormones and weight loss in overweight and obese individuals

Bisphenol A (BPA) and triclosan (TCS) were determined in urine of Belgian overweight and obese (n = 151) and lean (n = 43) individuals. After the first urine collection (0 M), obese patients started a diet program or have undergone bariatric surgery. Hereafter, three additional urine samples from obese patients were collected after 3 (3 M), 6 (6 M) and 12 (12 M) months. Both compounds were detected in > 99% of the samples. BPA had median concentrations of 1.7 and 1.2 ng/mL in obese and lean groups, respectively, while TCS had median concentrations of 1.5 and 0.9 ng/mL in the obese and lean groups, respectively. The obese group had higher urinary concentrations (ng/mL) of BPA (p < 0.5), while no significant differences were found for TCS between the obese and lean groups. No time trends between the different collection moments were observed. The BPA concentrations in the obese group were negatively associated with age, while no gender difference or relationship with body mass index was observed. For TCS, no relationships with gender, BMI, or age were found. The temporal variability of BPA and TCS was assessed with calculation of the intraclass correlation coefficient, Spearman rank correlation coefficients, and surrogate category analysis. We observed evidence that single spot urine samples might be predictive of exposure over a longer period of time. Dietary intakes of BPA and TCS did not differ significantly among the time points considered after obese individuals started losing weight (6 and 12 months). Multiple linear regression analyses after adjusting for age and weight loss revealed negative associations between urinary TCS and serum FT4 in the 0 M and 3 M female obese individuals and positive associations between urinary BPA and serum TSH in the lean group.     

A crossover–crossback prospective study of dibutyl-phthalate exposure from mesalamine medications and semen quality in men with inflammatory bowel disease

BackgroundPhthalates are widely used chemicals with ubiquitous exposure. Dibutyl-phthalate (DBP), a male reproductive toxicant in animals, is understudied in humans. Some mesalamine medications used to treat inflammatory bowel disease (IBD) have DBP in their coating, whereas other mesalamine formulations do not.ObjectivesTaking advantage of differences in mesalamine formulations, we investigated whether high-DBP exposure from mesalamine medications was associated with decreased semen parameters.Methods73 men with IBD taking mesalamine participated in a crossover-crossback prospective study. Men taking non-DBP containing mesalamine at baseline i.e., background exposure, crossed-over for four months to high-DBP mesalamine and then crossed-back for four months to their non-DBP mesalamine (B₁HB₂-arm;Background₁-High-Background₂) and vice versa for men taking high-DBP mesalamine at baseline (H₁BH₂-arm;High₁-Background-High₂). Men provided up to six semen samples (2: baseline, 2: crossover and 2: crossback).ResultsWe estimated crossover, crossback and carryover effects using linear mixed models adjusted for abstinence time, age, season and duration on high-DBP mesalamine at baseline. Semen parameters in B₁HB₂-arm (26 men, 133 samples) decreased after high-DBP mesalamine exposure (crossover versus baseline), especially motility parameters, and continued to decrease further even after crossback to non-DBP mesalamine (crossback versus crossover). The cumulative carryover effect of high-DBP (crossback versus baseline) was a decrease of % total sperm motility by 7.61(CI:− 13.1, − 2.15), % progressive sperm motility by 4.23(CI:− 8.05, − 0.4) and motile sperm count by 26.0% (CI:− 46.2%, 1.7%). However, H₁BH₂-arm (47 men, 199 samples) had no significant change during crossover or crossback.ConclusionsMen newly exposed to high-DBP mesalamine for four months had a cumulative reduction in several semen parameters, primarily sperm motility, that was more pronounced and statistically significant even after exposure ended for four months.     

Neighborhood deprivation,race/ethnicity,and urinary metal concentrations among young girls in California

BackgroundAlthough metals can adversely impact children's health, the distribution of exposures to many metals, particularly among vulnerable subpopulations, is not well characterized.ObjectivesWe sought to determine whether neighborhood deprivation was associated with urinary concentrations of thirteen metals and whether observed relationships varied by race/ethnicity.MethodsWe obtained neighborhood characteristics from the 2005–2009 American Community Survey. Demographic information and urine samples from 400 healthy young girls in Northern California were obtained during a clinical visit. Urine samples were analyzed for metals using inductively-coupled plasma-mass spectrometry and levels were corrected for creatinine. We ran analysis of variance and generalized linear regression models to estimate associations of urinary metal concentrations with neighborhood deprivation and race/ethnicity and stratified multivariable models to evaluate possible interactions among predictors on metals concentrations.ResultsUrinary concentrations of three metals (barium, lead, antimony) varied significantly across neighborhood deprivation quartiles, and four (barium, lead, antimony, tin) varied across race/ethnicity groups. In models adjusted for family income and cotinine, both race/ethnicity (F_3,224 = 4.34, p = 0.01) and neighborhood deprivation (F_3,224 = 4.32, p = 0.01) were associated with antimony concentrations, but neither were associated with lead, barium, or tin, concentrations. Examining neighborhood deprivation within race/ethnicity groups, barium levels (p_interaction < 0.01) decreased with neighborhood deprivation among Hispanic girls (p_trend < 0.001) and lead levels (p_interaction = 0.06) increased with neighborhood deprivation among Asian girls (p_trend = 0.04).ConclusionsOur results indicate that children's vulnerability to some metals varies by neighborhood deprivation quartile and race/ethnicity. These differential distributions of exposures may contribute to environmental health disparities later in life.     

Polymorphisms in ATP-binding cassette transporters associated with maternal methylmercury disposition and infant neurodevelopment in mother-infant pairs in the Seychelles Child Development Study

BackgroundATP-binding cassette (ABC) transporters have been associated with methylmercury (MeHg) toxicity in experimental animal models.AimsTo evaluate the association of single nucleotide polymorphisms (SNPs) in maternal ABC transporter genes with 1) maternal hair MeHg concentrations during pregnancy and 2) child neurodevelopmental outcomes.Materials and methodsNutrition Cohort 2 (NC2) is an observational mother-child cohort recruited in the Republic of Seychelles from 2008–2011. Total mercury (Hg) was measured in maternal hair growing during pregnancy as a biomarker for prenatal MeHg exposure (N = 1313) (mean 3.9 ppm). Infants completed developmental assessments by Bayley Scales of Infant Development II (BSID-II) at 20 months of age (N = 1331). Genotyping for fifteen SNPs in ABCC1, ABCC2 and ABCB1 was performed for the mothers.ResultsSeven of fifteen ABC SNPs (ABCC1 rs11075290, rs212093, and rs215088; ABCC2 rs717620; ABCB1 rs10276499, rs1202169, and rs2032582) were associated with concentrations of maternal hair Hg (p < 0.001 to 0.013). One SNP (ABCC1 rs11075290) was also significantly associated with neurodevelopment; children born to mothers with rs11075290 CC genotype (mean hair Hg 3.6 ppm) scored on average 2 points lower on the Mental Development Index (MDI) and 3 points lower on the Psychomotor Development Index (PDI) than children born to mothers with TT genotype (mean hair Hg 4.7 ppm) while children with the CT genotype (mean hair Hg 4.0 ppm) had intermediate BSID scores.DiscussionGenetic variation in ABC transporter genes was associated with maternal hair Hg concentrations. The implications for MeHg dose in the developing child and neurodevelopmental outcomes need to be further investigated.     

Associations between polycyclic aromatic hydrocarbon (PAH) exposure and oxidative stress in people living near e-waste recycling facilities in China

Emission of polycyclic aromatic hydrocarbons (PAHs) from e-waste recycling activities in China is known. However, little is known on the association between PAH exposure and oxidative damage to DNA and lipid content in people living near e-waste dismantling sites. In this study, ten hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) and two biomarkers [8-hydroxy-2′-deoxyguanosine (8-OHdG) and malondialdehyde (MDA)] of oxidative stress were investigated in urine samples collected from people living in and around e-waste dismantling facilities, and in reference population from rural and urban areas in China. The urinary levels of ∑₁₀OH-PAHs determined in e-waste recycling area (GM: 25.4 μg/g Cre) were significantly higher (p < 0.05) than those found in both rural (11.7 μg/g Cre) and urban (10.9 μg/g Cre) reference areas. The occupationally exposed e-waste workers (36.6 μg/g Cre) showed significantly higher (p < 0.01) urinary Σ₁₀OH-PAHs concentrations than non-occupationally exposed people (23.2 μg/g Cre) living in the e-waste recycling site. The differences in urinary Σ₁₀OH-PAHs levels between smokers (23.4 μg/g Cre) and non-smokers (24.7 μg/g Cre) were not significant (p > 0.05) in e-waste dismantling sites, while these differences were significant (p < 0.05) in rural and urban reference areas; this indicated that smoking is not associated with elevated levels of PAH exposure in e-waste dismantling site. Furthermore, we found that urinary concentrations of Σ₁₀OH-PAHs and individual OH-PAHs were significantly associated with elevated 8-OHdG, in samples collected from e-waste dismantling site; the levels of urinary 1-hydroxypyrene (1-PYR) (r = 0.284, p < 0.01) was significantly positively associated with MDA. Our results indicate that the exposure to PAHs at the e-waste dismantling site may have an effect on oxidative damage to DNA among selected participants, but this needs to be validated in large studies.     

DDTs in mothers' milk,placenta and hair,and health risk assessment for infants at two coastal and inland cities in China

This study is a one of the very few investigating the dichloro-diphenyl-trichloroethanes (DDTs) (summation of o,p′-DDE, p,p′-DDE, o,p′-DDD, p,p′-DDD, o,p′-DDT, and p,p′-DDT) in multiple human matrices in mothers' milk, placenta and hair collected from residents from two coastal cities: Guiyu (GY) and Taizhou (TZ) and one inland city: Lin'an (LA). TZ (milk: 360 ± 319 ng/g lipid wt.) showed significantly higher concentrations of DDTs than those from LA (milk: 190 ± 131 ng/g lipid wt.), whereas, concentrations of DDTs in GY (milk: 305 ± 109 ng/g lipid wt.) were in between TZ and LA. In addition, levels of DDTs in the human tissues from TZ (placenta: 122 ± 109 ng/g lipid wt.; hair: 79.9 ± 215 ng/g dry wt.) were significantly higher than those from Lin'an (placenta: 49.2 ± 30.2 ng/g lipid wt.; hair: 10.8 ± 7.09 ng/g dry wt.). The above concentrations of DDTs in milk exceeded the Codex Maximum Residue Limits/Extraneous Maximum Residue Limits for milk (20 ng/g lipid wt. whole milk), indicating that the human milk samples were grossly polluted. The present study revealed that human specimens collected from the coastal city (TZ) were more contaminated with inland one (LA), based on the levels of DDTs contained in samples which may be due to the higher dietary exposure to DDTs via consumption of contaminated seafood. The estimated daily intakes of DDTs by GY, TZ and LA infants were 1.69 ± 1.86, 1.48 ± 0.79, and 0.95 ± 0.73 μg/kg body wt./day, respectively which did not exceed 10 μg/kg body wt./day, the provisional tolerable daily intake proposed by the Food and Agriculture Organization/World Health Organization.     

Monocyclic and bicyclic monoterpenes in air of German daycare centers and human biomonitoring in visiting children,the LUPE 3 study

To investigate the assumed association between indoor air pollution with monoterpenes (MTps) and the internal MTp exposure of occupants, a comparative study was performed in daycare centers in two federal states of Germany. Three well-known monoterpenoid air pollutants, viz. α-pinene (αPN), Δ³-carene (CRN), and R-limonene (LMN), were measured in indoor air in 45 daycare centers. Additionally, urine samples of 222 children visiting these facilities were collected in the evening after a full-day stay. Altogether 11 MTp metabolites were analyzed in the urine samples using a novel highly sensitive and selective gas chromatographic–tandem-mass spectrometric procedure. The medians (95th percentiles) of the MTp levels in indoor air were 9.1 μg m^− 3 (94 μg m^− 3) for LMN, 2.6 μg m^− 3 (13 μg m^− 3) for αPN, and < 1.0 μg m^− 3 (3.2 μg m^− 3) for CRN. None of the day care centers exceeded the German health precaution or hazard guide value. In spite of the low MTp air exposure, the urine analyses revealed an exposure to the three monoterpenes in almost all children. The median levels of MTp metabolites in urine were 0.11 mg L^− 1 for LMN-8,9-OH, 0.10 mg L^− 1 for LMN-1,2-OH, 49 μg L^− 1 for PA, 2.9 μg L^− 1 for POH, 5.2 μg L^− 1 for tCAR, and 4.1 μg L^− 1 for cCAR (LMN metabolites), 7.2 μg L^− 1 for MYR, 19 μg L^− 1 for tVER, and 19 μg L^− 1 for cVER (αPN metabolites), as well as 8.2 μg L^− 1 for CRN-10-COOH (CRN metabolite). Statistically significant and strong correlations among the urinary metabolites of each MTp were found. Moreover, statistical associations between LMN metabolites and the LMN indoor air levels were revealed. However, the weakness of the associations indicates a considerable impact of other MTp sources, e.g. diet and consumer products, on the internal exposure.     

Pharmacokinetics of bisphenol A in humans following a single oral administration

BackgroundHuman exposures to bisphenol A (BPA) are widespread. The current study addresses uncertainties regarding human pharmacokinetics of BPA.ObjectiveTo reduce uncertainties about the metabolism and excretion of BPA in humans following oral administration.MethodsWe exposed six men and eight women to 100 μg/kg bw of deuterated BPA (d6-BPA) by oral administration and conducted blood and urine analysis over a three day period. The use of d6-BPA allowed administered d6-BPA to be distinguished from background native (unlabeled) BPA. We calculated the rate of oral absorption, serum elimination, half-life, area under the curve (AUC), urinary excretion, and metabolism to glucuronide and sulfate conjugates.ResultsMean serum total (unconjugated and conjugated) d6-BPA C_max of 1711 nM (390 ng/ml) was observed at T_max of 1.1 ± 0.50 h. Unconjugated d6-BPA appeared in serum within 5–20 min of dosing with a mean C_max of 6.5 nM (1.5 ng/ml) observed at T_max of 1.3 ± 0.52 h. Detectable blood levels of unconjugated or total d6-BPA were observed at 48 h in some subjects at concentrations near the LOD (0.001–0.002 ng/ml). The half-times for terminal elimination of total d6-BPA and unconjugated d6-BPA were 6.4 ± 2.0 h and 6.2 ± 2.6 h, respectively. Recovery of total administered d6-BPA in urine was 84–109%. Most subjects (10 of 14) excreted > 90% as metabolites within 24 h.ConclusionsUsing more sensitive methods, our study expands the findings of other human oral pharmacokinetic studies. Conjugation reactions are rapid and nearly complete with unconjugated BPA comprising less than 1% of the total d6-BPA in blood at all times. Elimination of conjugates into urine largely occurs within 24 h.     

Air pollution exposure and telomere length in highly exposed subjects in Beijing,China: A repeated-measure study

BackgroundAmbient particulate matter (PM) exposure has been associated with short- and long-term effects on cardiovascular disease (CVD). Telomere length (TL) is a biomarker of CVD risk that is modified by inflammation and oxidative stress, two key pathways for PM effects. Whether PM exposure modifies TL is largely unexplored.ObjectivesTo investigate effects of PM on blood TL in a highly-exposed population.MethodsWe measured blood TL in 120 blood samples from truck drivers and 120 blood samples from office workers in Beijing, China. We measured personal PM_2.5 and Elemental Carbon (EC, a tracer of traffic particles) using light-weight monitors. Ambient PM₁₀ was obtained from local monitoring stations. We used covariate-adjusted regression models to estimate percent changes in TL per an interquartile-range increase in exposure.ResultsCovariate-adjusted TL was higher in drivers (mean = 0.87, 95%CI: 0.74; 1.03) than in office workers (mean = 0.79, 95%CI: 0.67; 0.93; p = 0.001). In all participants combined, TL increased in association with personal PM_2.5 (+ 5.2%, 95%CI: 1.5; 9.1; p = 0.007), personal EC (+ 4.9%, 95%CI: 1.2; 8.8; p = 0.01), and ambient PM₁₀ (+ 7.7%, 95%CI: 3.7; 11.9; p < 0.001) on examination days. In contrast, average ambient PM₁₀ over the 14 days before the examinations was significantly associated with shorter TL (− 9.9%, 95%CI: − 17.6; − 1.5; p = 0.02).ConclusionsShort-term exposure to ambient PM is associated with increased blood TL, consistent with TL roles during acute inflammatory responses. Longer exposures may shorten TL as expected after prolonged pro-oxidant exposures. The observed TL alterations may participate in the biological pathways of short- and long-term PM effects.     

Novel exposure biomarkers of N,N-diethyl-m-toluamide (DEET): Data from the 2007–2010 National Health and Nutrition Examination Survey

BackgroundN,N-diethyl-m-toluamide (DEET) is a widely used insect repellent in the United States.ObjectivesTo assess exposure to DEET in a representative sample of persons 6 years and older in the U.S. general population from the 2007–2010 National Health and Nutrition Examination Survey.MethodsWe analyzed 5348 urine samples by using online solid-phase extraction coupled to isotope dilution-high-performance liquid chromatography-tandem mass spectrometry. We used regression models to examine associations of various demographic parameters with urinary concentrations of DEET biomarkers.ResultsWe detected DEET in ~ 3% of samples and at concentration ranges (> 0.08 μg/L–45.1 μg/L) much lower than those of 3-(diethylcarbamoyl)benzoic acid (DCBA) (> 0.48 μg/L–30,400 μg/L) and N,N-diethyl-3-hydroxymethylbenzamide (DHMB) (> 0.09 μg/L–332 μg/L). DCBA was the most frequently detected metabolite (~ 84%). Regardless of survey cycle and the person's race/ethnicity or income, adjusted geometric mean concentrations of DCBA were higher in May–Sep than in Oct–Apr. Furthermore, non-Hispanic whites in the warm season were more likely than in the colder months [adjusted odds ratio (OR) = 10.83; 95% confidence interval (CI), 3.28–35.79] and more likely than non-Hispanic blacks (OR = 3.45; 95% CI, 1.51–7.87) to have DCBA concentrations above the 95th percentile.ConclusionsThe general U.S. population, including school-age children, is exposed to DEET. However, reliance on DEET as the sole urinary biomarker would likely underestimate the prevalence of exposure. Instead, oxidative metabolites of DEET are the most adequate exposure biomarkers. Differences by season of the year based on demographic variables including race/ethnicity likely reflect different lifestyle uses of DEET-containing products.     

Human exposure pathways to organophosphate triesters — A biomonitoring study of mother–child pairs

The worldwide ban of several formulations of brominated flame retardants has caused an increase in the production of organophosphorus flame retardants (PFRs) to meet the existing fire regulations for a wide range of household products. This biomonitoring study surveys the occurrence of the metabolites from PFRs and related plasticizers (dialkyl and diaryl phosphates; DAPs) in urine from a Norwegian mother–child cohort (48 mothers and 54 children). Concentrations of DAPs were higher in the children than in their mothers (Wilcoxon signed-rank test p = 0.001). Median urinary concentrations of diphenyl phosphate (DPHP) were 1.1 and 0.51 ng/mL in children and mothers, respectively, followed by bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) with medians of 0.23 and 0.12 ng/mL, respectively. Detection frequencies for bis(2-butoxyethyl) phosphate (BBOEP) in urine from children and mothers were 32 and 1%, respectively (median < 0.18 ng/mL), and for di-n-butyl phosphate (DNBP) 15 and 8%, respectively (median < 0.12 ng/mL). The concentrations of DPHP and BDCIPP in urine from children were significantly correlated with those found for their parent compounds in air and dust from the households (Spearman's rank correlations 0.30 < R_s < 0.36; p < 0.05). For mothers, only the urinary concentration of BDCIPP was correlated to its precursor in dust from the households (R_s = 0.40; p < 0.01), which might indicate higher impact of the household environment on children than mothers. A diurnal variability study of the mothers' urinary concentrations of DPHP and BDCIPP showed lower concentrations at time periods when women were likely to be outside the household. In contrast, no relevant associations between organophosphate metabolites in urine and food consumption data obtained through a 24 hour recall were seen. This suggests that the residential environment is a more important exposure pathway to PFRs than the diet.     

Could exposure to phthalates speed up or delay pubertal onset and development? A 1.5-year follow-up of a school-based population

PurposePhthalates may interfere with the timing of pubertal development in adolescence and existing studies have shown inconsistent results. This study aims to assess the associations of pubertal onset and progression with urinary concentrations of phthalate metabolites in school-aged boys and girls.MethodsUsing isotope-dilution liquid chromatography tandem mass spectrometry, we analyzed 6 phthalate metabolites in urine samples of 430 children (222 boys and 208 girls) aged 9.7 ± 2.2 years (age range 6.1 to 13.8 years) at baseline and 18 months of follow-up. The associations of exposures to phthalates with pubertal development such as the testis, breast and pubic hair were evaluated using ordered logistic regression models, adjusting for baseline development stage, current chronological age, current body fat composition, and parental education.ResultsUrinary mono-n-butyl phthalate (MnBP) was associated with a 39% increase in the odds of presenting lower pubic hair development stages in boys, and mono (2-ethylhexyl) phthalate (MEHP) (p < 0.10), mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono (2-ethyl-5-oxohexyl) phthalate (MEOHP) were associated with 54%–65% increase in the odds of presenting higher breast development stages in girls (p < 0.05), while MEHHP and MEOHP were also associated with a 70% increase in the odds of menarche onset (p < 0.05). After adjusting for potential confounding variables, the associations of girls' pubertal onset with MnBP, MMP, MEP and MEHP were significant. The odds of girls' breast onset were 4 to 10 times higher in high MnBP, MMP, MEP or MEHP exposure group than in low exposure group.ConclusionsOur findings suggest subtle effects of phthalate metabolites associated with pubertal onset and progression. MnBP exposure may be associated with delayed pubic hair development in boys, while MnBP, MMP, MEP, and MEHP exposures may be associated with breast onset, and MEHP metabolites associated with speedup in breast development progression and earlier menarche onset in girls.     

Measurement and health risk assessment of PM2.5, flame retardants,carbonyls and black carbon in indoor and outdoor air in kindergartens in Hong Kong

Indoor air pollution is closely related to children's health. Polybrominated diphenyl ethers (PBDEs) and dechlorane plus (DP) transmitted through indoor PM_2.5 and dust, along with carbonyl compounds and black carbon (BC) aerosol were analysed in five Hong Kong kindergartens. The results showed that 60% of the median PM_2.5 levels (1.3 × 10¹ to 2.9 × 10¹ μg/m³ for indoor; 9.5 to 8.8 × 10¹ μg/m³ for outdoor) in the five kindergartens were higher than the guidelines set by the World Health Organization (2.5 × 10¹ μg/m³). Indoor PM_2.5 mass concentrations were correlated with outdoor PM_2.5 in four of the kindergartens. The PBDEs (0.10–0.64 ng/m³ in PM_2.5; 0.30–2.0 × 10² ng/g in dust) and DP (0.05–0.10 ng/m³ in PM_2.5; 1.3–8.7 ng/g in dust) were detected in 100% of the PM_2.5 and dust samples. Fire retardant levels in the air were not correlated with the levels of dust in this study. The median BC concentrations varied by > 7-fold from 8.8 × 10² ng/m^− 3 to 6.7 × 10³ ng/m^− 3 and cooking events might have caused BC concentrations to rise both indoors and outdoors. The total concentrations of 16 carbonyls ranged from 4.7 × 10¹ μg/m³ to 9.3 × 10¹ μg/m³ indoors and from 1.9 × 10¹ μg/m³ to 4.3 × 10¹ μg/m³ outdoors, whilst formaldehyde was the most abundant air carbonyl. Indoor carbonyl concentrations were correlated with outdoor carbonyls in three kindergartens. The health risk assessment showed that hazard indexes (HIs) HIs of non-cancer risks from PBDEs and DPs were all lower than 0.08, whilst non-cancer HIs of carbonyl compounds ranged from 0.77 to 1.85 indoors and from 0.50 to 0.97 outdoors. The human intake of PBDEs and DP through inhalation of PM_2.5 accounted for 78% to 92% of the total intake. The cancer hazard quotients (HQs) of formaldehyde ranged from 4.5E − 05 to 2.1E − 04 indoors and from 1.9E − 05 to 6.2E − 05 outdoors. In general, the indoor air pollution in the five Hong Kong kindergartens might present adverse effects to children, although different schools showed distinct pollution levels, so indoor air quality might be improved through artificial measures. The data will be useful to developing a feasible management protocol for indoor environments.     

Mercury and docosahexaenoic acid levels in maternal and cord blood in relation to segmental maternal hair mercury concentrations at parturition

Fish is a major source of harmful methylmercury (MeHg) and beneficial docosahexaenoic acid (DHA) in the developing brain. In this study, we investigated the correlations among maternal and umbilical cord (cord) MeHg and DHA levels at parturition, and mercury (Hg) concentration in 1-cm incremental segments hair samples which grew during gestation representing monthly MeHg exposure levels throughout the period. Whole blood Hg and plasma DHA levels were measured in blood sample pairs collected from 54 mothers at early gestation and parturition, and in cord blood. Maternal hair samples were collected at parturition, and Hg concentrations were measured in 1-cm incremental segments. Hg level in mothers at parturition was slightly lower than that at early gestation and the level in cord blood were approximately 1.9 times higher than that in mothers at parturition. On the other hand, DHA level in mothers at parturition was approximately 2.3 and 1.6 times higher than those in mothers at early gestation and in cord plasma, respectively. These results indicate that kinetics of these chemicals in mothers during gestation and placental transfer are completely different. However, Hg and DHA levels had significant positive correlation in fetal circulation. The cord blood Hg showed the strongest correlation with maternal hair Hg in the first 1-cm segment from the scalp at parturition (r = 0.87), indicating that fetal MeHg level reflects maternal MeHg burden at late gestation. In contrast, maternal and cord plasma DHA concentrations at parturition showed the highest correlation coefficients with Hg in the fifth (r = 0.43) and fourth (r = 0.38) 1-cm hair segments, suggesting that maternal and fetal DHA levels reflects maternal fish intake during mid-gestation.     

Polybrominated diphenyl ethers (PBDEs) in human samples of mother–newborn pairs in South China and their placental transfer characteristics

There are limited data concerning the placenta transfer characteristics and accumulation of polybrominated diphenyl ethers (PBDEs) in infants. However, PBDEs received increasing health concerns due to their endocrine disrupt and neurodevelopment toxicity effects. The present study assessed the accumulation of PBDEs in 30 paired placenta, breast milk, fetal cord blood, and neonatal urine samples collected from five major cities of the South China. The age of mothers ranged from 21 to 39 (mean 27.6 ± 4.56). The ∑ PBDE concentrations were 15.8 ± 9.88 ng g^− 1 lipid in placenta, 13.2 ± 7.64 ng g^− 1 lipid in breast milk, 16.5 ± 19.5 ng g^− 1 lipid in fetal cord blood, and 1.80 ± 1.99 ng ml^− 1 in neonatal urine. BDE-47 was the predominant congener in all types of human sample. Octa-BDEs such as BDE-196/-197 were detected highly in placenta and cord blood while moderately in breast milk and neonatal urine. Significant (p < 0.01) correlations were observed for both total and most individual PBDEs in cord blood–maternal placenta and breast milk–urine paired individual samples. The extent of placental transfer of higher brominated BDEs such as BDE-196/-197 was greater than that of BDE-47. The estimated daily intake (EDI) analysis for breast-fed infants revealed that newborns in these areas were exposed to relatively high levels of PBDEs via breast milk. Our study not only provided systematic fundamental data for PBDE distribution but also revealed the placenta transfer characteristics of PBDE congeners in South China.