Co-exposure to polycyclic aromatic hydrocarbons and nicotine and their associations with cognitive impairment risk in older adults from southern China

Exposure to polycyclic aromatic hydrocarbons (PAHs) and tobacco smoke is widespread and linked to various adverse health outcomes. Their potential to disturb the neurological system has raised much concern, particularly among older adults. Thus, we conducted a case-control study to assess the associations between co-exposure to PAHs and nicotine, and the risk of cognitive impairment and oxidative stress in older adults. A total of 384 adults aged 60 years and older were recruited from 2017 to 2018 in Shenzhen, China. Morning spot urine samples were collected for the analysis of 6 mono-hydroxylated PAHs, 8 nicotine metabolites, and a typical biomarker for oxidative stress, 8-hydroxy-2'-deoxyguanosine (8-OHdG). The Mini-Mental State Examination was used to assess the cognitive function of participants. Quantile-based g-computation (QGC), weighted quantile sum regression, and Bayesian kernel machine regression were used to analyze the associations between the exposure mixture and outcomes. QGC showed co-exposure to PAHs and nicotine were positively associated with cognitive impairment risk (OR: 1.66, 95% CI: 1.36-2.03, P < 0.001) and 8-OHdG (β:11.19, 95% CI: 3.90-18.48, P < 0.001). The primary contributors to cognitive impairment risk were (S)-nicotine-N-β-glucuronide (NicGluc), cotinine N-β-D-glucuronide (CotGluc) and (S)-cotinine N-oxide (CNO) and Cotinine (Cot), with no-linear dose-response relationships. However, 8-OHdG did not mediate the association between PAHs, nicotine and cognitive impairment risk.

Influence of dietary patterns on urinary excretion of cadmium in an Italian population: A cross-sectional study

INTRODUCTION

Cadmium is a toxic heavy metal with detrimental effects on human health. Apart from smoking and occupational factors, diet is the main source of cadmium. However, the relation between adherence to so-called "healthy" dietary patterns and cadmium exposure has not been investigated in detail. In this study, we aimed at assessing such association in a Northern Italian population.

METHODS

Using a cross-sectional study design, we investigated a population of non-smokers aged 30-60 years in the period 2017-2019. Each subject completed a validated food frequency questionnaire (FFQ) in order to estimate adherence to four dietary patterns, namely the Dietary Approach to Stopping Hypertension-DASH diet, Greek Mediterranean Index-GMI, the Italian Mediterranean Index-IMI, and the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet. We collected a fasting morning urinary sample to measure urinary levels of cadmium and cotinine. The association between increasing adherence to dietary patterns and cadmium exposure was evaluated using a cubic spline regression non-linear model and adjusting for relevant confounders (age, sex, body mass index, urinary cotinine levels, intake of fiber, and alcohol).

RESULTS

We recruited 137 participants (males/females: 62/75) with median (interquartile range-IQR) age of 47 (IQR: 43-53) years. Median scores for the investigated dietary patterns were 24 (IQR: 21-28), 4 (IQR: 3-6), 4 (IQR: 3-5), and 7.5 (IQR: 6.5-8.5) for DASH, GMI, IMI and MIND diets, respectively. The median urinary cadmium level was 0.21 μg/L (IQR: 0.11-0.34 μg/L). Spline regression analysis showed an inverse linear association between increasing adherence to the DASH and MIND diets and urinary cadmium levels, reaching a plateau at high adherence scores, approximately > 25 and > 9 for DASH and MIND diets, respectively. An increase of cadmium exposure with increasing MIND score also emerged. Conversely, the association was almost null for IMI, and slightly positive for GMI.

CONCLUSIONS

The present findings suggest that increasing adherence to the DASH and MIND diets are associated with decreased cadmium levels only at moderate level. Overall, these results indicate that public health strategies, including the decrease of cadmium contamination in healthy foods should be implemented.

Selenium exposure and urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine: Major effects of chemical species and sex

Selenium is an element present in trace amounts and different chemical forms. It may exert both beneficial and adverse effects on cellular redox status and on the generation of reactive oxygen species. 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxodG) is an oxidized derivative of deoxyguanosine, and a sensitive biomarker of oxidative stress and genotoxicity. The present study assessed the extent to which selenium status was associated with urinary 8-oxodG concentrations in a Northern Italian population. We recruited healthy, non-smoking blood donors living in the Reggio Emilia province during 2017-2019. We measured urinary 8-oxodG concentrations and used restricted cubic spline regression analyses to investigate the association between selenium status (estimated using food frequency questionnaires, urinary concentrations, and serum concentrations of selenium and selenium species) and 8-oxodG/g creatinine. Among 137 participants aged 30-60 years, median urinary selenium and 8-oxodG concentrations were 22.02 μg/L and 3.21 μg/g creatinine, respectively. Serum samples and selenium speciation analyses were available for 104 participants. Median total serum selenium levels and dietary intake were 116.5 μg/L and 78.7 μg/day, respectively. In spline regression analysis, there was little association between dietary, serum, or urinary selenium with 8-oxodG concentrations. In sex-specific analyses, urinary selenium showed a positive association with the endpoint among males. For single selenium species, we observed positive associations with urinary 8-oxodG for serum organic selenium species, and negative associations for inorganic selenium forms. In the most adjusted analysis, urinary 8-oxodG concentrations showed a strong positive association with selenomethione-bound selenium (Se-Met) and a negative association with inorganic tetravalent selenium, selenite. In sex-specific analyses, these associations were considerably stronger in males than in females. Overall, study findings indicate that selenium species exhibited very different patterns of associations with the biomarker of oxidative stress, and that these associations also depended on sex. Background exposure to Se-Met appears to be strongly and positively associated with oxidative stress.

Exposure to polycyclic aromatic hydrocarbons and the associations with oxidative stress in waste incineration plant workers from South China

Waste incineration is one of the most common emission sources of polycyclic aromatic hydrocarbons (PAHs), causing potential occupational exposure in waste incineration workers. However, relative investigations among waste incineration plant workers are still very limited, particularly in China. Therefore, we collected urine specimens from 77 workers in a waste incineration plant as the exposed group, and 101 residents as the control group in Shenzhen, China. Nine mono-hydroxylated PAH metabolites (OH-PAHs) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were measured, and their internal relationships were explored. The urinary levels of most OH-PAHs and 8-OHdG in the exposed group exhibited high levels versus another group (p < 0.05). We found negative associations between OH-PAHs and 8-OHdG in the control group (p < 0.05), while most of OH-PAHs were not associated with 8-OHdG in the exposed group, which indicated that the exposure to waste incineration could enlarge the level of individual oxidative stress damage. Nevertheless, PAHs were less likely to trigger obvious health risks in exposed workers through estimation of human intake and exposure risks. This study provides a reference for occupational PAH exposure and strengthen the need of health monitoring among incineration workers.

Associations of urinary and dietary cadmium with urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine and blood biochemical parameters

Cadmium is a heavy metal with established adverse effects on human health, namely on bone, liver and kidney function and the cardiovascular system. We assessed cadmium exposure and its correlation with biomarkers of toxicity. We recruited 137 non-smoking blood donors without a history of chronic disease or cancer who resided in the Northern Italy province of Reggio Emilia (mean age 47 years, range 30-60 years) in the 2017-2019 period. We used a semi-quantitative food frequency questionnaire to estimate dietary cadmium intake and urine samples to assess concentrations of urinary cadmium and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG). Median urinary cadmium and 8-oxodG concentrations were 0.21 μg/L (interquartile range (IQR): 0.11-0.34 μg/L) and 3.21 μg/g creatinine (IQR: 2.21-4.80 μg/g creatinine), respectively, while median dietary cadmium intake was 6.16 μg/day (IQR: 5.22-7.93 μg/day). We used multivariable linear and spline regression models to estimate mean differences exposure concentrations. Dietary and urinary cadmium were positively correlated, and both were positively and linearly correlated with 8-oxodG. We found a positive association of urinary cadmium with blood alanine aminotransferase (ALT), total cholesterol, low-density lipoprotein (LDL)-cholesterol and thyroid-stimulating hormone (TSH) concentrations. We also observed a positive association with triglycerides, in both linear (beta regression coefficient = 77.03, 95% confidence interval 32.27-121.78) and non-linear spline regression analyses. Despite the positive correlation between dietary and urinary cadmium estimates, dietary cadmium intake showed inconsistent results with the study endpoints and generally weaker associations, suggesting a decreased capacity to reflect actual cadmium exposure. Overall, these findings suggest that even low levels of cadmium exposure may adversely alter hematological and biochemical variables and induce oxidative stress.

Co-exposure to polycyclic aromatic hydrocarbons, benzene and toluene may impair lung function by increasing oxidative damage and airway inflammation in asthmatic children

As previous studies found that the direct associations between urinary polycyclic aromatic hydrocarbon (PAH), benzene and toluene (BT) metabolites and the decreased lung function were not conclusive, we further investigated relationship of oxidative damage and airway inflammation induced by PAHs and BTs exposure with lung function. A total of 262 children diagnosed with asthma and 72 heathy children were recruited. Results showed that asthmatic children had higher levels of PAHs and BTs exposure, as well as Malonaldehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) compared with healthy children. Furthermore, binary logistic regression showed that each unit increases in level of urinary 2-&3-hydroxyfluorene (2-&3-OHF), 2-hydroxyphenanthrene (2-OHPhe), 1-hydroxyphenanthrene (1-OHP) and S-phenylmercapturic acid (S-PMA) were significantly associated with an elevated risk of asthma in children with odds ratios of 1.5, 2.3, 1.7 and 1.4, respectively, suggesting that PAHs and BTs exposure could increase the risk of asthma for children. Neither PAH nor BT metabolite could comprehensively indicate the decreased lung function as only 2-&3-OHF and 1-OHP were significantly and negatively correlated with forced vital capacity (FVC). Moreover, levels of most individual PAH and BT metabolite were significantly correlated to MDA and 8-OHdG. Further hierarchical regression analysis indicated that MDA and 8-OHdG levels did not show significant effects on the decreased lung function, suggesting that they are not the suitable biomarkers to indirectly indicate the altered lung function induced by PAHs and BTs. Urinary 2-OHPhe and 1-&9-hydroxyphenanthrene (1-&9-OHPhe) were significantly correlated with fractional exhaled nitric oxide (FeNO). Moreover, FeNO significantly contributed to decreased lung function and explained 7.7% of variance in ratio of forced expiratory volume in 1 s (FEV₁) and FVC (FEV₁/FVC%). Hence, FeNO, rather than oxidative damage indicators or any urinary PAH and BT metabolite, is more sensitive to indirectly reflect the decreased lung function induced by PAHs and BTs exposure for asthmatic children.

Biological Monitoring of Occupational Exposure to Metals in Electric Steel Foundry Workers and Its Contribution to 8-Oxo-7,8-Dihydro-2'-Deoxyguanosine Levels

In this study, the urinary concentrations of selected metals in workers from an electric steel foundry in Tunisia were assessed and compared with existing biological limit values and general population reference values. Moreover, the association between oxidative DNA damage, measured as urinary 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxodG) and co-exposure to metals and polycyclic aromatic hydrocarbons (PAHs) was evaluated. Urinary levels of 12 metals were determined by inductively coupled plasma-mass spectrometry (ICP-MS) in end-shift spot samples from 89 workers. The urinary levels of phenanthrene (U-PHE), as marker of exposure to PAHs, and 8-oxodG were also available. Median levels ranged from 0.4 µg/L (cobalt, Co, and thallium, Tl) to 895 µg/L (zinc, Zn). Only 1% of samples was above the biological limit values for Co, and up to 13.5% of samples were above limit values for Cd. From 3.4% (Co) to 72% (lead, Pb) of samples were above the reference values for the general population. Multiple linear regression models, showed that manganese (Mn), Zn, arsenic (As), barium (Ba), Tl, and Pb were significant predictors of 8-oxodG (0.012 ≤ p ≤ 0.048); U-PHE was also a significant predictor (0.003 ≤ p ≤ 0.059). The variance explained by models was low (0.11 ≤ R2 ≤ 0.17, p < 0.005), showing that metals and PAHs were minor contributors to 8-oxodG. Overall, the comparison with biological limit values showed that the study subjects were occupationally exposed to metals, with levels exceeding biological limit values only for Cd.

Effect of exposure to phthalates on association of polycyclic aromatic hydrocarbons with 8-hydroxy-2'-deoxyguanosine

BACKGROUND

Although polycyclic aromatic hydrocarbons (PAHs) and phthalates separately related to oxidative DNA damage have been reported, the joint effect of them on oxidative DNA damage need to be evaluated.

METHODS

In this pilot study, 106 participants were recruited from the community-dwelling residents (n=1240) of Wuhan city, China. Each individual provided three continuous days of spot urine samples for measuring the urinary monohydroxylated PAHs (OH-PAHs), phthalates metabolites and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in the two seasons. Linear mixed effect model and Bayesian Kernel Machine Regression (BKMR) were used to analyze joint effect of urinary PAHs and phthalates metabolites on urinary 8-OHdG levels. We measured cellular and mitochondrial reactive oxygen species (ROS), malondialdehyde (MDA) and glutathione peroxidase (GSH-Px) levels as well as IL-6 and IL-8 secretions by the corresponding commercial kits in HepG2 cells treated with di (2-ethylhexyl) phthalate (DEHP, 62.5, 125.00, 250.00, 500.00 or 1000.00μM) alone, benzo[a]pyrene (BaP, 50.00μM) alone or both DEHP and BaP.

RESULTS

Linear mixed effect model showed that each of urinary PAHs metabolite was positively associated with urinary 8-OHdG levels; urinary level of mono (2-ethylhexyl) phthalate or monoisononyl phthalate was positively associated with urinary 8-OHdG levels; BKMR model indicated that a positive association of eight OH-PAHs with urinary 8-OHdG levels, nine urinary phthalates metabolites enhanced the association. We found that DEHP at the indicated concentration plus 50.00μM BaP increased cellular and mitochondrial ROS levels, IL-6 and IL-8 secretions at 24 and 48h as well as MDA levels and GSH-Px activities at 48h, compared to the solvent control.

CONCLUSIONS

Exposure to certain dose phthalates may attenuate the positive association of PAHs exposure with oxidative DNA damage in the body. DEHP at the certain concentrations enhanced BaP-induced mitochondrial ROS, pro-inflammatory response and the activation of the antioxidant defense system in HepG2 cells.