Long-term exposure assessment to phthalates: How do nail analyses compare to commonly used measurements in urine

From target analysis to suspect and non-target screening of endocrine-disrupting compounds in human urine

In the present work, a target analysis method for simultaneously determining 24 diverse endocrine-disrupting compounds (EDCs) in urine (benzophenones, bisphenols, parabens, phthalates and antibacterials) was developed. The target analysis approach (including enzymatic hydrolysis, clean-up by solid-phase extraction and analysis by liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS)) was optimized, validated and applied to volunteers’ samples, in which 67% of the target EDCs were quantified. For instance, benzophenone-3 (0.2–13 ng g⁻¹), bisphenol A (7.7–13.7 ng g⁻¹), methyl 3,5-dihydroxybenzoate (8–254 ng g⁻¹), mono butyl phthalate (2–17 ng g⁻¹) and triclosan (0.3–9 ng g⁻¹) were found at the highest concentrations, but the presence of other analogues was detected as well. The developed target method was further extended to suspect and non-target screening (SNTS) by means of LC coupled to high-resolution MS/MS. First, well-defined workflows for SNTS were validated by applying the previously developed method to an extended list of compounds (83), and then, to the same real urine samples. From a list of approximately 4000 suspects, 33 were annotated at levels from 1 to 3, with food additives/ingredients and personal care products being the most abundant ones. In the non-target approach, the search was limited to molecules containing S, Cl and/or Br atoms, annotating 4 pharmaceuticals. The results from this study showed that the combination of the lower limits of detection of MS/MS and the identification power of high-resolution MS/MS is still compulsory for a more accurate definition of human exposome in urine samples.

Di-n-butyl phthalate promotes monocyte recruitment via miR-137-3p-SP1-MCP-1 pathway

Since non-covalent bound character and widespread application in numerous products, people are exposed to di-n-butyl phthalate (DBP) at low levels through various ways. Epidemiological studies suggested an association between DBP exposure and atherosclerosis (AS). Still, molecular mechanisms remain unclear. This study aimed to explore the effects of DBP on monocyte recruitment, a key and initial step of AS. EA.hy926 cells were treated with DBP (10-9-10-5 M) or DMSO as control. Chemotaxis assay was applied to investigate THP-1 recruitment. Expression of mRNA /miRNAs and proteins were measured by qRT-PCR and Western blotting, respectively. Levels of monocyte chemotactic protein 1 (MCP-1) in supernatant were detected by ELISA assay. Receptor internalization assay was performed to confirm C-C chemokine receptor type 2 (CCR2) subcellular localization in THP-1 cells and the binding between CCR2 and MCP-1. Dual-luciferase reporter assay was used to analyze the combination between miR-137-3p and specificity protein 1 (SP1), as well as SP1 and MCP-1. Results showed that number of recruited THP-1 cells after EA.hy926 cells treated by DBP was significantly higher than that in the control group due to promoted MCP-1 expression. In addition, expression of MCP-1 was regulated through miR-137-3p-SP1 cascade. Besides, overexpression of miR-137-3p reversed the increased number of recruited THP-1 cells. Our results implied that DBP might promote THP-1 recruitment by targeting miR-137-3p-SP1-MCP-1 in EA.hy926 cells.

PAHs and their hydroxylated metabolites in the human fingernails from e-waste dismantlers: Implications for human non-invasive biomonitoring and exposure

Non-invasive human biomonitoring methods using hair and fingernails as matrices are widely used to assess the exposure of organic contaminants. In this work, a total of 72 human fingernails were collected from workers and near-by residents from a typical electronic waste (e-waste) dismantling site, and were analyzed for human exposure to polycyclic aromatic hydrocarbons (PAHs) and their mono-hydroxyl metabolites (OH-PAHs). The concentrations of PAHs and OH-PAHs were obtained as 7.97-551 and 39.5-3280 ng/g for e-waste workers (EW workers), 7.05-431 and 27.3-3320 ng/g for non-EW workers, 7.93-289 and 124-779 ng/g for adult residents, and 8.88-1280 and 181-293 ng/g for child residents, respectively. The composition profiles of PAHs in the human fingernails of the four groups were similar, with isomers of Phe, Pyr and Fluo being the predominated congeners, while 2-OH-Nap accounted for more than 70% of the total OH-PAHs. These contaminants were found most in the fingernails of EW workers, followed by non-EW workers, adult residents, and child residents, indicating e-waste dismantling activities are the major sources of PAH exposure. However, significantly higher levels of PAHs with 4-6 rings were observed only in workers as opposed to the residents, and a significant correlation between 3-OH-Flu (p < 0.05) and 2-OH-Phe (p < 0.01) in the fingernails and urine was observed, but no significant correlation was found between the concentration of OH-PAHs in matched hair and fingernail samples. In addition, the levels of PAHs in fingernails increased with the age of EW workers. This is the first study to explore the accumulation and distribution of PAHs and OH-PAHs in human fingernails, which would provide valuable insight into non-invasive biomonitoring and health risk assessment of PAHs.

A critical review on human internal exposure of phthalate metabolites and the associated health risks

Phthalates (PAEs) are popular synthetic chemicals used as plasticizers and solvents for various products, such as polyvinyl chloride or personal care products. Human exposure to PAEs is associated with various diseases, resulting in PAE biomonitoring in humans. Inhalation, dietary ingestion, and dermal absorption are the major human exposure routes. However, estimating the actual exposure dose of PAEs via an external route is difficult. As a result, estimation by internal exposure has become the popular analytical methods to determine the concentrations of phthalate metabolites (mPAEs) in human matrices (such as urine, serum, breast milk, hair, and nails). The various exposure sources and patterns result in different composition profiles of PAEs in biomatrices, which vary from country to country. Nevertheless, the mPAEs of diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), di-iso-butyl phthalate (DiBP), and di-(2-ethylhexyl) phthalate (DEHP) are predominant in the urine. These mPAEs have greater potential health risks for humans. Children have been observed to exhibit higher exposure risks to several mPAEs than adults. Besides age, other influencing factors for phthalate exposure are gender, jobs, and residential areas. Although many studies have reported biological monitoring of PAEs, only a few reviews that adequately summarized the reports are available. The current review appraised available studies on mPAE quantitation in human biomatrices and estimated the dose and health risks of phthalate exposure. While some countries lack biomonitoring data, some countries' data do not reflect the current PAE exposure. Thence, future studies should involve frequent PAE biomonitoring to accurately estimate human exposure to PAEs, which will contribute to health risk assessments of human exposure to PAEs. Such would aid the formulation of corresponding regulations and restrictions by the government.

Paraben concentrations in human fingernail and its association with personal care product use

Parabens are used as antimicrobial preservatives in a range of consumer products. However, very limited information is available about the association between use of personal care products and paraben burden in human tissues. Accumulation of parabens in some non-destructive biomarkers (such as human fingernail) is essential for paraben biomonitoring. In this study, 50 human fingernail samples were collected from Nanjing, China. A subset of participants (n = 32) also provided their face cream samples (as the representative of personal care products). Six parabens, including methyl- (MeP), ethyl- (EtP), propyl- (PrP), butyl- (BuP), heptyl- (HeP), and benzyl-parabens (BzP), together with their major metabolites were measured in the fingernail and face cream samples. Total concentrations of parabens and their major metabolites were 39.9-27400 ng/g in fingernails. MeP, PrP and EtP were the three dominant parabens in fingernails with median values of 3140, 1290, and 127 ng/g, respectively. Significantly higher levels in female fingernails than those in male fingernails were observed for MeP, PrP, EtP, BuP, and the MeP metabolite (methyl protocatechuate, OH-MeP) (p < 0.05). Adult fingernails contained greater concentrations of MeP and PrP than juvenile fingernails (p < 0.05). Positive correlations were observed for EtP (R = 0.36, p < 0.05) and BuP (R = 0.48, p = 0.008) concentrations between the fingernail and face cream samples. Our work is a preliminary study trying to explore the quantitative relationship between paraben concentrations in human body and use of personal care products. The result here provides a direct evidence that use of personal care products is one of the major sources for human exposure to parabens.

Polybrominated diphenyl ethers and decabromodiphenyl ethane in paired hair/serum and nail/serum from corresponding chemical manufacturing workers and their correlations to thyroid hormones, liver and kidney injury markers

We detected the polybrominated diphenyl ethers (PBDEs) or decabromodiphenyl ethane (DBDPE) in paired hair-serum and nail-serum samples collected from the corresponding chemical manufacturing workers. The levels of decabrominated diphenyl ether (BDE-209) or DBDPE in the serum, hair and nail samples were all significantly higher than those reported in other studies, and the "work place" (pretreatment or posttreatment workshop) was the primary influencing factor that affected the levels of specific BFRs in vivo. For BDE-209 workers, the BDE-209 in both the hair and nail samples were significantly and positively related to the BDE-209 in the serum, indicating that both hair and nails can be used as noninvasive biomatrices to reflect internal exposure to BDE-209. In DBDPE workers, hair rather than nails was more suitable for use as a noninvasive biomatrix to infer the DBDPE exposure level. A series of serum biomarkers reflecting thyroid hormones and liver and kidney injuries were tested to calculate the correlations between hair or nail BFR levels and the levels of the biomatrices. The BDE-209 in the hair samples was significantly and positively correlated with the total protein (TP), and the nail BDE-209 level was significantly and positively related to the total bilirubin (TBIL), indirect bilirubin (IDBIL) and uric acid (UA). The DBDPE in hair was significantly and positively correlated with the thyroid hormones free triiodothyronine (fT3) and total triiodothyronine (tT3) and kidney injury markers, including blood urea nitrogen (BUN), creatinine (CRE) and cystatin C (Cys-C). In addition, the nail DBDPE levels were significantly and positively correlated with the albumin/globulin (A/G), BUN, CRE and Cys-C but negatively correlated with the TP and globulin (GLO). Our findings provide preliminary evidence that hair and nails can be used as noninvasive biomatrices for assessing internal BFR exposure and health damage in occupational workers.

Quantitative identification of and exposure to synthetic phenolic antioxidants, including butylated hydroxytoluene, in urine

Synthetic phenolic antioxidants (SPAs) such as 2,6-di-tert-butyl-4-hydroxytoluene (butylated hydroxytoluene, BHT), are used in a wide variety of consumer products, including certain foodstuffs (e.g. fats and oils) and cosmetics. Although BHT is considered generally safe as a food preservative when used at approved concentrations, there is debate whether BHT exposure is linked to cancer, asthma, and behavioral issues in children. Little is known with regard to human exposure to SPAs and the methods to measure these chemicals in urine. In this study, six SPAs and the metabolites were analyzed in 145 urine samples collected from four Asian countries (China, India, Japan, and Saudi Arabia) and the United States. BHT was found in 88% of the urine samples at median and maximum concentrations of 1.26 and 15 ng/mL, respectively. BHT metabolites and butylated hydroxyanisole (BHA) were found in 39% to 89% of the urine samples at a concentration range of Collapse

Key Words

• BHT
• Biomarker
• Biomonitoring
• Exposure
• Synthetic phenolic antioxidant
• Urine

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MESH Headings

• Adult
• Antioxidants/analysis
• Butylated Hydroxytoluene/analysis
• Child
• Environmental Exposure/analysis
• Humans
• Phenols/urine

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Grants

• U2C ES026542 NIEHS NIH HHS

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Affiliation(s)

Wei Wang Wadsworth Center, New York State Department of Health, and Department of Environmental Health Sciences, School of Public Health, State University of New York at Albany, Empire State Plaza, P.O. Box 509, Albany, NY 12201-0509, United States

Kurunthachalam Kannan Wadsworth Center, New York State Department of Health, and Department of Environmental Health Sciences, School of Public Health, State University of New York at Albany, Empire State Plaza, P.O. Box 509, Albany, NY 12201-0509, United States; Biochemistry Department, Faculty of Science, and Experimental Biochemistry Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia.

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The extent and predictors of phthalate exposure among couples undergoing in vitro fertilization treatment

Phthalates are chemicals used as plasticizers and solvents in many consumer products but are suspected of disrupting the endocrine system and are known for their reproductive/developmental health risks. This study examined the extent and predictors of phthalate exposure among 599 couples undergoing in vitro fertilization. A questionnaire was administered to obtain sociodemographic, health, and lifestyle data, and two spot urine samples were collected from the couples to analyze eight phthalate metabolites, cotinine (COT) as a smoking index, and creatinine to adjust for urine dilution. Seven phthalate metabolites were detected in > 94% of the urine samples, and monobenzyl phthalate (MBzP) was found in 24% of the women and 26% of their male partners. Median phthalate levels were highest for monoethyl phthalate (MEP), at 333.26 μg/l in women and 290 μg/l in male partners, and lowest for MBzP, at 1.17 μg/l in women and 1.14 μg/l in male partners. Correlation coefficients of ≥ 0.4 between the women and their male partners for the eight urinary phthalate metabolites may indicate a shared source of exposure. A multivariate regression model was used to assess the association between predictors and each urinary phthalate metabolite. Several potential predictors for the variations in specific urinary phthalate metabolites were identified, including the body mass index, age, socioeconomic status, and regional distribution for both women and their male partners but with slightly different patterns. Women with a history of breastfeeding, using bottled water for cooking and storing food in plastic bags had lower MEP (8.7%), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP) (9.2%), and both mono-iso-butyl phthalate and MECPP (8.2 and 8.1%). A history of contraceptive use was associated with an increase in MECPP (8.7%), mono-(2-ethyl-5-hydroxyhexyl) phthalate (11.4%), mono-(2-ethyl-5-oxohexyl) phthalate (7.6%), and the molar sum of bis (2-ethylhexyl) phthalate metabolites (8.9%). Urinary COT levels were associated with an increase of 10-16% in all urinary metabolites in women but of only 10.5% in mono-(2-ethylhexyl) phthalate in male partners. More than 95% of the couples reported the use of cosmetics, perfumes, and personal-care products, but we were not able to find associations with urinary phthalate metabolites, perhaps due to their short half-lives. MEP levels associated with the use of household cleaning products were 11.2% higher in male partners. Our levels were generally higher than those reported elsewhere, perhaps due to different lifestyles, cultural practices, dietary habits, use of personal-care products, and governmental legislation.

Synthetic phenolic antioxidants and their major metabolites in human fingernail

Synthetic phenolic antioxidants (SPAs) have been widely used in foods, polymers, and cosmetics, but very limited information is available about their occurrence in human tissues. In this study, five SPAs, namely 2,6-di-tert-butyl-4-methylphenol (BHT), 2-tert-butyl-4-hydroxyanisole (BHA), propyl-, octyl-, and dodecyl-gallate (PG, OG, and DG), and four major metabolites of BHT, including 3,5-di-tert-butyl-4 -hydroxybenzaldehyde (BHT-CHO), 2,6-di-tert-butyl-4-(hydroxymethyl) phenol (BHT-OH), 3,5-di-tertbutyl-4-hydroxybenzoic acid (BHT-COOH), and 2,6-di-tert-butyl-1,4-benzoquinone (BHT-Q), were determined in human fingernail samples collected from Nanjing, China. Total concentrations of the nine target analytes (∑₉SPAs) were 523-14,000 ng/g. BHT was the predominant SPA compound and detected in all samples at a range of 309-11,400 ng/g. The ∑₉SPAs was negatively correlated with age of fingernail donors (p < 0.05). In addition, indoor dust samples from the living places of the fingernail providers were collected with aim to better understand the SPA exposure pathways. A positive correlation (p < 0.05) was found only for DG concentrations between paired fingernail and dust samples, while not for other SPAs, suggesting that SPAs accumulated in fingernails may not be mainly from indoor dust. SPAs were measured for the first time in human fingernail, and the elevated concentrations in fingernail suggest that the health risk of SPAs should be paid more attention due to their bioaccumulation potential in human body. Further studies are warranted about exposure pathway, distribution and metabolism of SPAs in human body.

Assessment of lead exposure among automobile technicians in Khyber Pakhtunkhwa, Pakistan

Exposure to Pb among automobile technicians in selected towns of Khyber Pakhtunkhwa Province, Pakistan, was studied using a questionnaire, biological sampling (blood, hair, nails), and analysis of Pb biomonitoring data across various subgroups of occupation, age, and years of exposure. The study population included exposed automobile technicians (n=50) and a control group (n=50). The automobile technicians were further stratified into 4 groups: mechanics, auto-body technicians, electricians, and painters. Mean Pb levels in biological samples of the automobile technicians were significantly higher than in the control group (P<0.01). The Pb concentrations (mean±standard deviation) in whole blood, hair, and nails of automobile technicians were 65.3±41.9μgdL^-1, 23.6±11.2mgkg^-1 and 29.7±14.5mgkg^-1, respectively, whereas concentrations in the control group were 21.7±17.6μgdL^-1, 4.8±3.4mgkg^-1 and 7.2±3.9mgkg^-1. Fifty two percent of the automobile technicians had blood levels >50μgdL^-1, but only 14% of the control group exceeded this level. Considering that Pb blood levels of 50μgdL^-1 exceed maximum concentrations recommended by leading public health organizations, appropriate measures should be taken to protect the welfare of the exposed automobile technicians and their families.

Case Study on Screening Emerging Pollutants in Urine and Nails

Alternative plasticizers and flame retardants (FRs) have been introduced as replacements for banned or restricted chemicals, but much is still unknown about their metabolism and occurrence in humans. We identified the metabolites formed in vitro for four alternative plasticizers (acetyltributyl citrate (ATBC), bis(2-propylheptyl) phthalate (DPHP), bis(2-ethylhexyl) terephthalate (DEHTP), bis(2-ethylhexyl) adipate (DEHA)), and one FR (2,2-bis (chloromethyl)-propane-1,3-diyltetrakis(2-chloroethyl) bisphosphate (V6)). Further, these compounds and their metabolites were investigated by LC/ESI-Orbitrap-MS in urine and finger nails collected from a Norwegian cohort. Primary and secondary ATBC metabolites had detection frequencies (% DF) in finger nails ranging from 46 to 95%. V6 was identified for the first time in finger nails, suggesting that this matrix may also indicate past exposure to FRs as well as alternative plasticizers. Two isomeric forms of DEHTP primary metabolite were highly detected in urine (97% DF) and identified in finger nails, while no DPHP metabolites were detected in vivo. Primary and secondary DEHA metabolites were identified in both matrices, and the relative proportion of the secondary metabolites was higher in urine than in finger nails; the opposite was observed for the primary metabolites. As many of the metabolites present in in vitro extracts were further identified in vivo in urine and finger nail samples, this suggests that in vitro assays can reliably mimic the in vivo processes. Finger nails may be a useful noninvasive matrix for human biomonitoring of specific organic contaminants, but further validation is needed.

Autopsy tissues as biological monitors of human exposure to environmental pollutants. A case study: Concentrations of metals and PCDD/Fs in subjects living near a hazardous waste incinerator

Human biomonitoring is of tremendous importance to prevent potential adverse effects derived from human exposure to chemicals. Blood and urine are among the biological monitors more frequently used. However, biological matrices such as breast milk, hair, nails, saliva, feces, teeth, and expired air are also often used. In addition, and focused mainly on long-term exposure, adipose tissue and other human tissues like bone, liver, brain or kidney, are also used as biological monitors of certain substances, especially for long-term biomonitoring. However, for this kind of tissues sampling is always a limiting factor. In this paper, we have examined the role of autopsy tissues as biological monitors of human exposure to environmental pollutants. For it, we have used a case study conducted near a hazardous waste incinerator (HWI) in Catalonia (Spain), in which the concentrations of metals and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), have been periodically determined in autopsy tissues of subjects living in the area under potential influence of the facility. This case study does not show advantages -in comparison to other appropriate biomonitors such as blood- in using autopsy tissues in the monitoring of long-term exposure to metals and PCDD/Fs.

Estimating uptake of phthalate ester metabolites into the human nail plate using pharmacokinetic modelling

There is a lack of knowledge regarding uptake of phthalate esters (PEs) and other chemicals into the human nail plate and thus, clarity concerning the suitability of human nails as a valid alternative matrix for monitoring long-term exposure. In particular, the relative importance of internal uptake of phthalate metabolites (from e.g. blood) compared to external uptake pathways is unknown. This study provides first insights into the partitioning of phthalate-metabolites between blood and nail using pharmacokinetic (PK) modelling and biomonitoring data from a Norwegian cohort. A previously published PK model (Lorber PK model) was used in combination with measured urine data to predict serum concentrations of DEHP and DnBP/DiBP metabolites at steady state. Then, partitioning between blood and nail was assessed assuming equilibrium conditions and treating the nail plate as a tissue, assuming a fixed lipid and water content. Although calculated as a worst-case scenario at equilibrium, the predicted nail concentrations of metabolites were lower than the biomonitoring data by factors of 44 to 1300 depending on the metabolite. It is therefore concluded that internal uptake of phthalate metabolites from blood into nail is a negligible pathway and does not explain the observed nail concentrations. Instead, external uptake pathways are more likely to dominate, possibly through deposition of phthalates onto the skin/nail and subsequent metabolism. Modelling gaseous diffusive uptake of PEs from air to nail revealed that this pathway is unlikely to be important. Experimental quantification of internal and external uptake pathways of phthalates and their metabolites into the human nail plate is needed to verify these modelling results. However, based on this model, human nails are not a good indicator of internal human exposure for the phthalate esters studied.