Photodegradation of hydroxyfluorenes in ice and water: A comparison of kinetics, effects of water constituents, and phototransformation by-products.

The photochemical behavior of organic pollutants in ice is poorly studied in comparison to aqueous photochemistry. Here we report a detailed comparison of ice and aqueous photodegradation of two representative OH-PAHs, 2-hydroxyfluorene (2-OHFL) and 9-hydroxyfluorene (9-OHFL), which are newly recognized contaminants in the wider environment including colder regions. Interestingly, their photodegradation kinetics were clearly influenced by whether they reside in ice or water. Under the same simulated solar irradiation (λ > 290 nm), OHFLs photodegraded faster in ice than in equivalent aqueous solutions and this was attributed to the specific concentration effect caused by freezing. Furthermore, the presence of dissolved constituents in ice also influenced photodegradation with 2-OHFL phototransforming the fastest in 'seawater' ice (k = (11.4 ± 1.0) × 10-2 min-1) followed by 'pure-water' ice ((8.7 ± 0.4) × 10-2 min-1) and 'freshwater' ice ((8.0 ± 0.7) × 10-2 min-1). The presence of dissolved constituents (specifically Cl-, NO3-, Fe(III) and humic acid) influences the phototransformation kinetics, either enhancing or suppressing phototransformation, but this is based on the quantity of the constituent present in the matrixes, the specific OHFL isomer and the matrix type (e.g., ice or aqueous solution). Careful derivation of key photointermediates was undertaken in both ice and water samples using tandem mass spectrometry. Ice phototransformation exhibited fewer by-products and 'simpler' pathways giving rise to a range of hydroxylated fluorenes and hydroxylated fluorenones in ice. These results are of importance when considering the fate of PAHs and OH-PAHs in cold regions and their persistence in sunlit ice.

Association between polycyclic aromatic hydrocarbons and thyroid function among males and females: data from NHANES 2007-2008.

The objective of this study was to evaluate the association between thyroid function and exposure to selected polycyclic aromatic hydrocarbons (PAH) among those aged ≥ 20 years. Thyroid variables considered for evaluation were thyroid-stimulating hormone, free and total serum thyroxine (FT4, TT4), free and total triiodothyronine (FT3, TT3), and thyroglobulin. PAH metabolites in urine for which data were analyzed were 1-hydroxynaphthalene, 2-hydroxynaphthalene, 2-hydroxyfluorene, 3-hydroxyfluorene, 9-hydroxyfluorene, 1-hydroxyphenanthrene, 2-hydroxyphenanthrene, 3-hydroxyphenanthrene, and 1-hydroxypyrene. Using data from 2007 to 2008 National Health and Nutrition Examination Survey, regression models with logs of thyroid variables as dependent variables and PAH exposure, age, race/ethnicity, iodine sufficiency, smoking status, and others as independent variables were fitted. For females, increased levels of 2-hydroxynapthalene, 2-hydroxyphenanthrene, and 1-hydroxypyrene were associated with elevated levels of TT3. For males, increased levels of 1-hydroxyphenanthrene, 2-hydroxyphenanthrene, and 9-hydroxypyrene were associated with decreased levels of FT4.

Mass spectrometric characterization of urinary hydrafinil metabolites for routine doping control purposes.

Little information on the human metabolism and urinary elimination of hydrafinil (9-fluorenol) exists. In order to support preventive anti-doping activities concerning compounds such as hydrafinil, a pilot elimination study was conducted with three healthy male volunteers receiving a single oral dose of 50 mg of hydrafinil. Urine samples were collected prior to and up to 72-h post-administration and were subjected to both gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry, which allowed for the identification of the intact drug as well as Phase I and Phase II metabolites, primarily hydroxylated and/or glucuronidated or sulfo-conjugated hydrafinil. The identity of these metabolites was corroborated by high-resolution/high-accuracy tandem mass spectrometry, and the applicability of routine doping control workflows for the detection of hydrafinil and its main metabolites was assessed. Therefore, two findings of hydrafinil and its metabolites were recorded, which concerned out-of-competition doping control samples and, hence, were not pursued with confirmatory analyses. Yet, the initial testing procedure results indicate that hydrafinil might require consideration in sports drug testing programs to ensure its detection, if classified as prohibited by the World Anti-Doping Agency (WADA).

Association of Urinary Polycyclic Aromatic Hydrocarbons and Diabetes in Korean Adults: Data from the Korean National Environmental Health Survey Cycle 2 (2012-2014).

PURPOSE: To investigate the associations between the urinary levels of polycyclic aromatic hydrocarbons (PAHs) and diabetes mellitus in Korean adults. MATERIALS AND METHODS: We examined the data of 6478 participants aged ≥19 years from the Korean National Environmental Health Survey (KoNEHS) cycle 2 (2012-2014). The urinary levels of 1-hydroxypyrene (1-OHP), 2-naphthol (2-NAP), 1-hydroxyphenathrene (1-OHPhe), and 2-hydroxyfluorene (2-OHFlu) were measured by gas chromatography-mass spectrometry. Diabetes mellitus was defined as a self-report of physician-diagnosed diabetes mellitus or the use of oral hypoglycemics or insulin. Analyses were adjusted for sex, age, body mass index, household income, alcohol consumption, physical activity, urinary creatinine and cotinine, menopausal status, and quartiles of all other PAHs. RESULTS: The prevalence of diabetes was 6.5% in the study population. In men, the geometric means of the 2-NAP and 2-OHFlu levels were higher in participants with diabetes mellitus than in those without diabetes mellitus [4.11 vs 3.26 µg/L (P <0.05) and 0.45 vs 0.40 µg/L (P <0.05), respectively]. In women, the geometric mean of 2-NAP levels was also higher in participants with diabetes mellitus than in those without diabetes mellitus (1.81 vs 0.56 µg/L, P <0.05), but there were no significant differences in geometric means for other PAHs. A higher odds ratio (OR) of diabetes was found in participants with the highest quartiles of urinary 2-NAP [OR 1.83, 95% confidence interval (CI) 1.29-2.60] and 2-OHFlu (OR 1.81, 95% CI 1.10-2.98) than in those with the lowest quartiles. CONCLUSION: The urinary 2-NAP and 2-OHFlu levels were associated with diabetes mellitus in Korean adults. Further studies are needed to determine a potential causal relationship between PAH exposure and diabetes mellitus and its underlying mechanism.

Association between polycyclic aromatic hydrocarbons and osteoporosis: data from NHANES, 2005-2014.

The association between osteoporosis and polycyclic aromatic hydrocarbons was not clear. However, recent studies showed that both osteoporosis and polycyclic aromatic hydrocarbons were associated with reactive oxygen species. So we presumed that polycyclic aromatic hydrocarbons were associated with increased odds of osteoporosis. We found 3-hydroxyfluorene was associated with decreased odds of osteoporosis, while 2-hydroxyfluorene was associated with increased odds of osteoporosis. PURPOSE: Previous studies showed that polycyclic aromatic hydrocarbons were involved in the production of reactive oxygen species that played an important role in illness. Other studies demonstrated that the reactive oxygen species might play a role in occurrence of osteoporosis. However, the association between polycyclic aromatic hydrocarbons and osteoporosis was not clear. Therefore, we conducted a study to investigate the relationship between polycyclic aromatic hydrocarbons and osteoporosis. METHODS: A total of 3053 individuals aged 50 years or older were drawn from National Health and Nutritional Examination Survey, 2005-2014. Eight polycyclic aromatic hydrocarbons metabolites (1-hydroxynaphthalene, 2-hydroxynaphthalene, 2-hydroxyfluorene, 3-hydroxyfluorene, 1-hydroxyphenanthrene, 2-hydroxyphenanthrene, and 3-hydroxyphenanthrene and 1-hydroxypyrene) were examined to represent exposure of polycyclic aromatic hydrocarbons in the body. Weighted percentage and weighted mean were used to describe classified variable and continuous variable, respectively. We used weighted logistic regression to estimate the association of polycyclic aromatic hydrocarbons and osteoporosis. RESULTS: Five hundred seventy-seven (18.9%) osteoporosis patients were included. Among the eight polycyclic aromatic hydrocarbons metabolites, 3-hydroxyfluorene was associated with decreased odds of osteoporosis after controlling socio-demographic status, body mass index, alcohol, previous fracture, parental fracture, glucocorticoid use, dietary calcium intake, smoking, and other polycyclic aromatic hydrocarbons metabolites (OR = 0.63, 95%CI 0.41-0.98). 2-hydroxyfluorene (OR = 1.87, 95%CI 1.07-3.29) was associated with increased odds of osteoporosis. In the nonsmoking group, we found the association of osteoporosis with 2-hydroxyfluorene (OR = 2.56, 95%CI 1.10-5.96) and 3-hydroxyfluorene (OR = 0.41, 95%CI 0.22-0.77) still exists. CONCLUSION: Our study found that 3-hydroxyfluorene was associated with decreased odd of osteoporosis, while 2-hydroxyfluorene was associated with increased odds of osteoporosis. Our study was a cross-sectional study, therefore cohort studies or experimental studies about association of PAH and osteoporosis is needed.

Comparison of gaseous polycyclic aromatic hydrocarbon metabolites according to their specificity as biomarkers of occupational exposure: Selection of 2-hydroxyfluorene and 2-hydroxyphenanthrene.

Exposure to Polycyclic Aromatic Hydrocarbons (PAHs) occurs by respiratory, digestive and dermal absorption. Biomonitoring takes all pathways into account but sensitive and specific biomarkers are required. Different gaseous PAHs metabolites were used due to their abundance in the atmospheric mixtures but none of them were selected as better biomarker than the others. To identify the best candidates for assessing occupational airborne exposure, relation between atmospheric levels of Naphtalene, Fluorene and Phenanthrene and urinary metabolites concentrations was studied in a carbon electrode workers group. Linear mixed effects models were built to select explanatory variables and estimate variance component. Urinary creatinine was a predictor of metabolites levels confirming the importance of diuresis for interpreting results. High significance of pre-shift sampling time combined with positive coefficients of post-shift indicated that urine should be sampled at the end of the workday in association with pre-shift urine to avoid misinterpretations. Among the 10 metabolites studied, urinary 2-hydroxyfluorene and 2-hydroxyphenanthrene showed the highest increase of variance explained by models after inclusion of individual atmospheric levels as explanatory variable. Priority could be given to 2-hydroxyfluorene due to higher excretion levels than 2-hydroxyphenanthrene.

Regression models to estimate the total concentration of polycyclic aromatic hydrocarbon metabolites in urine.

Polycyclic aromatic hydrocarbons (PAH) are potentially mutagenic and carcinogenic and as such their exposure is of serious concern. Regression models to estimate the total concentration of polycyclic aromatic hydrocarbon metabolites (∑PAH) in urine were developed. Using data from National Health and Nutrition Examination Survey for the years 2003-2008 and 2011-2012, regression models were developed to estimate ∑PAH in urine. The performance of the fitted models were computed by comparing percent predicted values located between 0 and 5%, 5-10%, 15-20% and >20% of the observed values. While data for 2003-2008 were used to fit the regression models, the data for 2011-2012 were solely used to evaluate the performance of the fitted models. R(2) of the fitted model was 94.7%. About 46% of the predicted values for the 2003-2008 data and over 48% of the predicted values for the 2011-2012 data were found to be between 0 and 10% of the observed values. In order to use these models, in addition to age, gender, and smoking status, and optionally race/ethnicity, the knowledge of the levels of only 1-hydroxynaphthalene, 2-hydroxynaphthalene, and 9-hydroxyfluorene is necessary. Models that optionally require the knowledge of the levels of urine creatinine were also developed.

Aqueous photochemical degradation of hydroxylated PAHs: Kinetics, pathways, and multivariate effects of main water constituents.

Hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) are contaminants of emerging concern in the aquatic environment, so it is of great significance to understand their environmental transformation and toxicity. This study investigated the aqueous photochemical behavior of four OH-PAHs, 9-Hydroxyfluorene (9-OHFL), 2-Hydroxyfluorene, 9-Hydroxyphenanthrene and 1-Hydroxypyrene, under simulated sunlight irradiation (λ>290 nm). It was observed that their photodegradation followed the pseudo-first-order kinetics. Based on the determined quantum yields, their calculated solar apparent photodegradation half-lives in surface waters at 45° N latitude ranged from 0.4min for 9-Hydroxyphenanthrene to 7.5 × 10(3)min for 9-OHFL, indicating that the OH-PAHs would intrinsically photodegrade fast in sunlit surface waters. Furthermore, 9-OHFL as an example was found to undergo direct photolysis, and self-sensitized photooxidation via OH rather than (1)O2 in pure water. The potential photoreactions involved photoinduced hydroxylation, dehydrogenation and isomerization based on product identification by GC-MS/MS. 9-OHFL photodegraded slower in natural waters than in pure water, which was attributed to the integrative effects of the most photoreactive species, such as Fe(III), NO3(-), Cl(-) and humic acid. The photomodified toxicity was further examined using Vibrio fischeri, and it was found that the toxicity of photolyzed 9-OHFL did not decrease significantly (p>0.05) either in pure water or in seawater, implying the comparable or higher toxicity of some intermediates. These results are important for assessing the fate and risks of OH-PAHs in surface waters.

Studying the effects of polycyclic aromatic hydrocarbons on peripheral arterial disease in the United States.

PURPOSE: Polycyclic aromatic hydrocarbons are a group of prevalent pollutants which are produced by incomplete combustion of organic materials such as coal, fuel, tobacco smoking and food cooking. The associations between exposures to polycyclic aromatic hydrocarbons (PAHs) and peripheral arterial disease (PAD) have not been well studied. METHODS: We used the 2001-2004 National Health and Nutrition Examination Survey (NHANES) to investigate the associations between eight monohydroxy urinary metabolites of four PAHs and PAD. RESULTS: In a logistic regression model, subjects within the middle and highest tertiles of fluorene metabolites, 2-hydroxyfluorene (2-FLUO) and 3-hydroxyfluorene (3-FLUO), and phenanthrene metabolites, 1-hydroxyphenanthrene (1-PHEN) and 2-hydroxyphenanthrene (2-PHEN), had significantly higher prevalence of PAD as compared to subjects within the lowest tertile after adjusting for cigarette smoking, diabetes mellitus and other covariates (For 2-FLUO, the 3rd tertile: OR=2.22, 95% CI=1.13-4.37, p for trend=0.02; For 3-FLUO, the 3rd tertile: OR=2.36, 95% CI: 1.16-4.77, p for trend=0.02; For 1-PHEN, the 3rd tertile: OR=1.84, 95% CI: 1.01-3.37, p for trend=0.04; For 2-PHEN, the 3rd tertile: OR=1.76, 95% CI: 1.07-2.88, p for trend=0.03). CONCLUSIONS: Our findings suggest that exposure to PAHs may increase the risk of PAD. Further studies are necessary to explore the associations between PAHs and PAD.

Bacterial Reduction of 9-Fluorenone to 9-Hydroxyfluorene.

A wild type of the Gram-positive bacterium, Bacillus brevis, reduced polycyclic aromatic compounds such as 9-fluorenone to the corresponding alcohol, 9-hydroxyfluorene, at 30°C in an anaerobic atmosphere in a 97% yield by extraction with an organic solvent. The products could be also continuously isolated by dialysis from a flowing reaction solution.