A yearlong monitoring campaign of polycyclic aromatic compounds and other air pollutants at three sites in Sweden: Source identification, in vitro toxicity and human health risk assessment.

Air pollution is a complex mixture of gases and particulate matter (PM) with local and non-local emission sources, resulting in spatiotemporal variability in concentrations and composition, and thus associated health risks. To study this in the greater Stockholm area, a yearlong monitoring campaign with in situ measurements of PM10, PM1, black carbon, NOx, O3, and PM10-sampling was performed. The locations included an Urban and a Rural background site and a Highway site. Chemical analysis of PM10 was performed to quantify monthly levels of polycyclic aromatic compounds (PACs), which together with other air pollution data were used for source apportionment and health risk assessment. Organic extracts from PM10 were tested for oxidative potential in human bronchial epithelial cells. Strong seasonal patterns were found for most air pollutants including PACs, with higher levels during the winter months than summer e.g., highest levels of PM10 were detected in March at the Highway site (33.2 µg/m3) and lowest in May at the Rural site (3.6 µg/m3). In general, air pollutant levels at the sites were in the order Highway > Urban > Rural. Multivariate analysis identified several polar PACs, including 6H-Benzo[cd]pyren-6-one, as possible discriminatory markers for these sites. The main sources of particulate pollution for all sites were vehicle exhaust and biomass burning emissions, although diesel exhaust was an important source at the Highway site. In vitro results agreed with air pollutant levels, with higher oxidative potential from the winter samples. Estimated lung cancer cases were in the order PM10 > NO2 > PACs for all sites, and with less evident seasonal differences than in vitro results. In conclusion, our study presents novel seasonal data for many PACs together with air pollutants more traditionally included in air quality monitoring. Moreover, seasonal differences in air pollutant levels correlated with differences in toxicity in vitro.

Non-additive mixture effects of benzo[a]pyrene and pesticides in vitro and in vivo: Role of AhR signaling.

Polycyclic aromatic hydrocarbons (PAHs) and pesticides are two major groups of environmental contaminants which humans are simultaneously exposed to. However, potential mixture interactions of these groups of chemicals are not well-studied. In this study, the effects of binary mixtures of the PAH benzo[a]pyrene (B[a]P) and the commonly used pesticides chlorpyrifos, paraquat and tebuconazole on human liver HepG2 cells were investigated. The results showed that binary mixtures of B[a]P and paraquat or tebuconazole mainly caused additive effects on cell viability and cytochrome P4501a1 (CYP1A1) expression compared to single compound exposures. In contrast, the binary mixture with chlorpyrifos interacted antagonistically on cell viability and ROS production, whereas synergistic effects were observed for induction of CYP1A1 expression. B[a]P and chlorpyrifos also inhibited the activity of recombinant human CYP1A1 enzyme. To verify the synergistic in vitro results, zebrafish (Danio rerio) embryos were exposed to binary mixtures of B[a]P and chlorpyrifos. The mixtures caused synergistic induction of CYP1A expression, as well as synergistic developmental toxicity on multiple endpoints including non-inflated swim bladder, yolk-sac and pericardial edema, and spinal deformation. The effects were reduced upon morpholino-mediated knockdown of the aryl hydrocarbon receptor (AhR), indicating an AhR-dependence of the synergistic toxicity. Altogether, these data suggest that the combination of AhR activation and CYP1A1 inhibition is responsible for the underlying non-additive interaction between B[a]P and chlorpyrifos in vitro and in vivo.

Investigation of the toxicity of a glyphosate-based herbicide in a human liver cell line: Assessing the involvement of Nrf2 pathway and protective effects of vitamin E and α-lipoic acid.

Glyphosate-based herbicides (GBHs) are the most widely used herbicides all over the world and has gained more attention in recent years because of health safety concerns. In this study, Roundup, one of the most popular glyphosate formulations, was used to evaluate cytotoxic, oxidative stress and apoptosis inducing effects of GBHs in a human hepatocellular cell line (HepG2). Roundup was shown to significantly increase cellular reactive oxygen species (ROS) levels, which lead to activation of the nuclear factor-erythroid-2-related factor 2 (Nrf2) antioxidant defense pathway including reduced levels of heme oxygenase 1 (HO-1). Furthermore, Roundup was found to induce apoptosis and further analysis confirmed involvement of a mitochondrial-dependent pathway verified by increased Bax/Bcl-2 ratios. Investigation of the protective effects of antioxidants vitamin E (Vit E) and α-lipoic acid (LA) against Roundup toxicity showed that both antioxidants significantly reduced the cytotoxicity, ROS formation, HO-1 downregulation, and apoptosis and that Vit E did so more efficiently than LA. In conclusion, our findings highlight the ROS producing and apoptosis inducing effects associated with GBHs, the activation of Nrf2 pathway as a defense mechanism and the protective effects of Vit E and LA against GBH toxicity.

In vitro cytotoxicity and genotoxicity of single and combined pesticides used by Bolivian farmers.

We previously showed that farmers in Bolivia are exposed to many pesticides, some at elevated levels, and that this was associated with increased risk of genetic damage. To improve the understanding of possible mixture effects, the cytotoxicity and genotoxicity of pesticides were studied in vitro using human liver HepG2 cells. The studied pesticides were 2,4-D, chlorpyrifos, cypermethrin, glyphosate, methamidophos, paraquat, profenofos, and tebuconazole. Three mixtures (U1, U2, and U3) were based on profiles of urinary pesticide metabolites and one mixture on the most frequently used pesticides (S1). The results showed that paraquat and methamidophos were the most cytotoxic pesticides (EC50 ≤0.3 mM). Paraquat, chlorpyrifos, tebuconazole, and the U1, U2, and U3 mixtures, which contained a large proportion of either chlorpyrifos or tebuconazole, significantly increased intracellular ROS levels. Most pesticides activated DNA damage signaling through proteins Chk1 and H2AX. Strongest responses were elicited by paraquat, profenofos, chlorpyrifos, cypermethrin, and the S1 mixture, which contained 25% paraquat. Comet assay revealed significant increases of DNA damage in response to paraquat, cypermethrin, and U2 and S1 mixtures, which contained high levels of cypermethrin and paraquat, respectively. In summary, we showed that the tested pesticides, alone or in mixtures, in general induced oxidative stress and that most pesticides, and especially paraquat and cypermethrin, were genotoxic in HepG2 cells. We could also show that mixtures dominated by these two pesticides displayed a marked genotoxic potency, which agreed with our previous population studies.

Assessment of perfluoroalkyl substances levels in tap and bottled water samples from Turkey.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) draw considerable attention for their potential toxic effects in humans and environment. Drinking water is accepted as one of the major exposure pathways for PFASs. In this study, we measured concentrations of 10 perfluoroalkyl substances in 94 tap water samples collected in two different sampling periods (August 2017 and February 2018) from 33 provinces of Turkey, as well as in 26 different brands of plastic and glass-bottled water samples sold in supermarkets in Turkey. Perfluorohexanoic acid (PFHxA), perfluorobutane sulfonate (PFBS) and perfluoropentanoic acid (PFPeA) were the most frequently detected PFASs in the samples of tap waters. The maximum concentrations in tap waters were measured as 2.90, 2.37, 2.18, 2.04, and 1.93 ng/L, for PFHxA, perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), and perfluorobutanoic acid (PFBA), respectively. The most abundant perfluorinated chemical in tap water samples was PFBA with 17%, followed by PFOS (13%), PFBS (12%), perfluoroheptanoic acid (PFHpA) (11%), PFHxA (11%), and PFOA (11%). The total PFASs concentration in tap water ranged from 0.08 to 11.27 ng/L. As regards bottled waters, the concentrations of PFASs were generally lower than those in tap water samples. These results revealed that tap water samples in Turkey might be considered generally safe based on the established guidelines around the world. However, due to their persistence and potential to accumulate and reach higher concentrations in the environment, careful monitoring of PFASs in all types of water is critical.