Case study approach to modeling historical disinfection by-product exposure in Iowa drinking waters

In the 1980 s, a case–control epidemiologic study was conducted in Iowa(USA) to analyze the association between exposure to disinfection by-products(DBPs) and bladder cancer risk. Trihalomethanes(THMs), the most commonly measured and dominant class of DBPs in drinking water, served as a primary metric and surrogate for the full DBP mixture.Average THM exposure was calculated, based on rough estimates of past levels in Iowa. To reduce misclassification, a follow-up study was undertaken to improve estimates of past THM levels and to re-evaluate their association with cancer risk. In addition, the risk associated with haloacetic acids, another class of DBPs, was examined. In the original analysis, surface water treatment plants were assigned one of two possible THM levels depending on the point of chlorination. The re-assessment considered each utility treating surface or groundwater on a case-by-case basis. Multiple treatment/disinfection scenarios and water quality parameters were considered with actual DBP measurements to develop estimates of past levels. The highest annual average THM level in the re-analysis was156 μg/L compared to 74 μg/L for the original analysis. This allowed the analysis of subjects exposed at higher levels( 96 μg/L). The re-analysis established a new approach, based on case studies and an understanding of the water quality and operational parameters that impact DBP formation, for determining historical exposure.     

The accident-exposure association: self-reported versus recorded collisions

Problem

It has been claimed that exposure to risk of road traffic accidents (usually conceptualized as mileage) is curvilinearly associated with crashes (i.e., the increase in number of crashes decreases with increased mileage). However, this effect has been criticized as mainly an artifact of self-reported data.

Method

To test the proposition that self-reported accidents create part of the curvilinearity in data by under-reporting by high-accident drivers, self-reported and recorded collisions were plotted against hours of driving for bus drivers.

Results

It was found that the recorded data differed from self-reported information at the high end of exposure, and had a more linear association with the exposure measure as compared to the self-reported data, thus supporting the hypothesis.

Discussion

Part of the previously reported curvilinearity between accidents and exposure is apparently due to biased methods. Also, the interpretation of curvilinearity as an effect of exposure upon accidents was criticized as unfounded, as the causality may just as well go the other way. Impact on industry: The question of how exposure associates with crash involvement is far from resolved, and everyone who uses an exposure metric (mileage, time, induced) should be careful to investigate the exact properties of their variable before using it.     

Biological monitoring of chlorpyrifos exposure to rice farmers in Vietnam

Chlorpyrifos is the most common organophosphate insecticide registered for use in Vietnam and is widely used in agriculture, particularly rice farming. However, chlorpyrifos exposure to and adverse effects on farmers has not been evaluated. In this study, biological monitoring of chlorpyrifos exposure in a group of rice farmers was conducted after a typical application event using back-pack spraying.Urine samples (24 h) were collected from the rice farmers before and post insecticide application. Samples were analysed for 3,5,6-trichloropyridinol (TCP), the major urinary metabolite of chlorpyrifos, using an enzymatic pre-treatment before extraction followed by HPLC-MS/MS. Absorbed Daily Dose (ADD) of chlorpyrifos for farmers were then estimated from urinary TCP levels, expressed as μg g⁻¹ creatinine. The analytical method for urinary TCP had a low detection limit (0.6 μg L⁻¹), acceptable recovery values (80-114%), and low relative percentage differences in duplicate and repeated samples.Post-application chlorpyrifos ADD of farmers varied from 0.4 to 94.2 μg kg⁻¹ (body weight) d⁻¹ with a mean of 19.4 μg kg⁻¹ d⁻¹ which was approximately 80-fold higher than the mean baseline exposure level (0.24 μg kg⁻¹ d⁻¹). Hazard Quotients (ratio of the mean ADD for rice farmers to acute oral reference dose) calculated using acute oral reference doses recommended by United States and Australian agencies varied from 2.1 (Australian NRA), 4.2 (US EPA) to 6.9 (ATSDR).Biological monitoring using HPLC-MS/MS analysis of urinary TCP (24 h) was found to be an effective method for measuring chlorpyrifos exposure among farmers. This case study found that Vietnamese rice farmers had relatively high exposures to chlorpyrifos after application, which were likely to have adverse health effects.     

Vulnerability and adaptation to climate risks in Ontario agriculture

A vulnerability approach to climate change adaptation research is employed to explore prospects of agricultural adaptation to climatic variability and change. The methodological approach focuses on the system of concern, in this case, farms in Perth County, Ontario. Twenty-five interviews and four focus groups with farmers were used to identify climate risks on farms, and to document farmers’ responses to conditions and risks associated with climate and weather. The information collected describes a complex decision-making environment, with many forces both external and internal to the farm operation influencing management decisions. Within this environment, climate and weather are consistently referred to as a significant force influencing both farm operations and management decisions. Farmers have, however, developed a wide-range of anticipatory and reactive management strategies to manage climate risks. While these have potential to address future climate-related risks and opportunities, there are limits to adaptation, and an increase in the frequency of extreme events may exceed their adaptive capacities. Farmers are also generally unaware and/or unconcerned about future climate change, which could constrain opportunities to adopt long-term climate change adaptations.     

Bioaccessibility of polychlorinated biphenyls in different foods using an in vitro digestion method

Bioaccessibility of organic pollutants in food is important for exposure estimation and risk assessment. An in vitro enzyme digestion experiment was carried out to analyze the bioaccessibility of PCBs in different foods including freshwater fish (bighead carp and oriental weather fish) and vegetables (spinach and cabbage). The results indicated that the bioaccessibility of PCBs in freshwater fish (3%) was much lower than that in leafy vegetables (25%). Based on field survey, the daily exposure TEQ value from these two types of food was 17.9 pg/kg bw/day. However, when bioaccessibility was taken into consideration, the value decreased to 0.61 pg/kg bw/day. Therefore, the forms of PCBs existing in food strongly influenced the bioavailability for humans, which may have important implications on dietary exposure. To our knowledge, this is the first paper to illustrate the bioaccessibility of PCBs in different foods using an in vitro digestion method.     

Exposure to air pollutants in Vietnam: Assessing potential risk for tourists

Tourism can form an important component of a nation's GDP,and Vietnam is among the most visited countries in Southeast Asia.Most studies on personal exposure focus on the general population,or occupational cohorts with exposure to specific pollutants.However,short-term exposure to air pollutants while visiting regions with high levels of air pollution can lead to acute health effects.A personal exposure study was conducted across three cities in Vietnam to estimate exposure to particulate matter(PM_(2.5)) and black carbon for tourists.Measurements were conducted during the wet season in 2014 in Ho Chi Minh City,Da Lat and Nha Trang using portable instrumentation.Average 24-hr PM_(2.5) and BC exposures were estimated as 18.9 ± 9.24 and 3.41 ± 1.33 μg/m~3 and among the three cities,Ho Chi Minh was found to have the highest PM_(2.5) concentrations.Environmental tobacco smoke,commuting and street food stands were found to contribute to highest levels of exposure to PM_(2.5) and BC across all cities.     

Dislodgeable residues of profenofos on jasmine and risk assessment of post application exposure to flower bud pickers

A field study was conducted to measure the dislodgeable residues of profenofos applied to jasmine (Jasminum sambac) and risk assessment was done for laborers engaged in picking of flower buds. Profenofos was applied at 0.10, 0.15, and 0.20% concentration and the jasmine bud samples were analysed for residues using GC. The initial deposit of 1.6–3.8, 3.8–7.1, and 5.2–7.6 µg cm^?2 was detected on jasmine buds at 0.10, 0.15, and 0.20% concentration, respectively. At the recommended dose of 0.10%, the half-life was 1–2 days and the dislodgeable residues disappeared within 7 days. The results indicate faster disappearance of dislodgeable residues on jasmine buds. Risk assessment was done based on dislodgeable foliar residues and exposure estimates based on surrogate data and expressed as Margin of Exposure (MOE). The entry restrictions for exposure of jasmine flower pickers to profenofos, would be at least, 1 day following application, for the recommended concentration of 0.10% (MOE = 106) and 3 days, at higher concentrations of 0.15% (MOE = 156) and 0.20% (MOE = 115).     

Concentrations of PFOS, PFOA and other perfluorinated alkyl acids in Australian drinking water

Perfluorinated alkyl acids (PFAAs) are persistent environmental pollutants, found in the serum of human populations internationally. Due to concerns regarding their bioaccumulation, and possible health effects, an understanding of routes of human exposure is necessary. PFAAs are recalcitrant in many water treatment processes, making drinking water a potential source of human exposure. This study was conducted with the aim of assessing the exposure to PFAAs via potable water in Australia. Sixty-two samples of potable water, collected from 34 locations across Australia, including capital cities and regional centers. The samples were extracted by solid phase extraction and analyzed via liquid chromatography/tandem mass spectrometry for a range of perfluoroalkyl carboxylates and sulfonates. PFOS and PFOA were the most commonly detected PFAAs, quantifiable in 49% and 44% of all samples respectively. The maximum concentration in any sample was seen for PFOS with a concentration of 16 ng L⁻¹, second highest maximums were for PFHxS and PFOA at 13 and 9.7 ng L⁻¹. The contribution of drinking water to daily PFOS and PFOA intakes in Australia was estimated. Assuming a daily intake of 1.4 and 0.8 ng kg⁻¹ bw for PFOS and PFOA the average contribution from drinking water was 2-3% with a maximum of 22% and 24% respectively.     

Triclosan in individual human milk samples from Australia

Triclosan is a chlorinated phenol ether that has been in widespread use as a broad-spectrum antibacterial agent for four decades. When compared to the limited international data available on human body burden of triclosan, results from a pooled blood study suggested that triclosan concentrations in Australia were a factor two higher than observed in Sweden. This study determined triclosan levels in individual human milk samples (n = 151) collected between 2002 and 2005 from primiparous Australian mothers. It provided the first report of population triclosan levels and individual variation in Australia and gave a measure of infant exposure via breast feeding. The distribution of triclosan concentration was positively skewed, with 7.2% of the samples below the LOQ, 66% with a concentration of less than or equal to 1.0 ng g⁻¹ fresh weight and the remaining samples above 1 ng g⁻¹ reaching a maximum concentration of 19 ng g⁻¹ fresh weight. The mean and median triclosan concentrations were 1.3 ± 2.7 ng g⁻¹ f.w. and 0.26 ng g⁻¹ f.w., respectively. The results of this study showed high variability in triclosan concentrations between individuals and no correlations with maternal age (p = 0.094), maternal weight (p = 0.971) or infant age at the time of sample collection (p = 0.621). A large number of samples contained low or non-quantifiable concentrations of triclosan and so, in Australia, ubiquitous background exposure due to environmental sources is low. This means that body burden can be influenced by an individual’s use of triclosan containing product. Given that triclosan containing product use is continuing, it is important that monitoring in both humans and the environment is continued and that triclosan containing products are adequately labeled so that an individual can choose to avoid exposure.     

Urinary and serum metabolites of di-n-pentyl phthalate in rats

Di-n-pentyl phthalate (DPP) is used mainly as a plasticizer in nitrocellulose. At high doses, DPP acts as a potent testicular toxicant in rats. We administered a single oral dose of 500 mg kg⁻¹ bw of DPP to adult female Sprague-Dawley rats (N = 9) and collected 24-h urine samples 1 d before and 24- and 48-h after DPP was administered to tentatively identify DPP metabolites that could be used as exposure biomarkers. At necropsy, 48 h after dosing, we also collected serum. The metabolites were extracted from urine or serum, resolved with high performance liquid chromatography, and detected by mass spectrometry. Two DPP metabolites, phthalic acid (PA) and mono(3-carboxypropyl) phthalate (MCPP), were identified by using authentic standards, whereas mono-n-pentyl phthalate (MPP), mono(4-oxopentyl) phthalate (MOPP), mono(4-hydroxypentyl) phthalate (MHPP), mono(4-carboxybutyl) phthalate (MCBP), mono(2-carboxyethyl) phthalate (MCEP), and mono-n-pentenyl phthalate (MPeP) were identified based on their full scan mass spectrometric fragmentation pattern. The ω − 1 oxidation product, MHPP, was the predominant urinary metabolite of DPP. The median urinary concentrations (μg mL⁻¹) of the metabolites in the first 24 h urine collection after DPP administration were 993 (MHPP), 168 (MCBP), 0.2 (MCEP), 222 (MPP), 47 (MOPP), 26 (PA), 16 (MPeP), and 9 (MCPP); the concentrations of metabolites in the second 24 h urine collection after DPP administration were significantly lower than in the first collection. We identified some urinary metabolic products in the serum, but at much lower levels than in urine. Because of the similarities in metabolism of phthalates between rats and humans, based on our results and the fact that MHPP can only be formed from the metabolism of DPP, MHPP would be the most adequate DPP exposure biomarker for human exposure assessment. Nonetheless, based on the urinary levels of MHPP, our preliminary data suggest that human exposure to DPP in the United States is rather limited.