Maximum Exposure Concentrations Research Articles

Growth inhibition of offspring larvae caused by the maternal transfer effects of tetrabromobisphenol A in zebrafish

Tetrabromobisphenol A (TBBPA) is an industrial chemical and the most widely used brominated flame retardant, and has raised environmental health concerns. However, the maternal transfer toxicity of TBBPA is less studied in fish despite its frequency in the water environment, and limited evidence exists to confirm the major contributing factors. In this study, we performed a 28-d experiment on female and male zebrafish exposed to TBBPA (0, 5, 50, and 500 μg/L), and shortened body length of offspring larvae was observed at the maximum exposure concentration. By cross-mating control and exposed zebrafish (male or female), our results showed that the observed growth inhibition in the progeny was attributed to the maternal transfer effect. Although 28-d exposure resulted in the existence of TBBPA in ovaries and ova, the maternal transfer of TBBPA was not responsible for the shortened body length of offspring larvae, as evidenced through TBBPA embryo microinjection. Moreover, proteomic analyses in ova indicated that the abundance of apolipoproteins (apoa1, apoa1b, apoa2, apoa4b, and apoc1) was significantly downregulated in the ova, which may be partially responsible for the shortened body length of offspring larvae. Interestingly, these proteins did not differentially express in the ovaries. Therefore, our results demonstrate that TBBPA exposure disturbed maternal protein transfer from the ovaries to the ova, providing novel insights into the underlying maternal transfer effects.

An optical sensor for the sensitive determination of formaldehyde gas based on chromotropic acid and 4-aminoazobenzene immobilized in a hydrophilic membrane.

Formaldehyde is a common contaminant in occupational and environmental atmospheres, prolonged exposure leads to health risks, and its determination is necessary to protect health. There is a great demand for portable, rapid, and sensitive methods that can be used in resource-limited settings. In this respect, a colorimetric sensor has been developed based on the colour change from pink to purple of co-immobilized chromotropic acid and 4-aminoazobenzene in hydroxypropyl methylcellulose when it is exposed to different concentrations of formaldehyde. The concentration of formaldehyde in the gas phase was quantified by measuring the change of the appropriate colour coordinates in response to the concentration of formaldehyde. A calibration curve was obtained for formaldehyde, with a useful concentration range from 0.08 to 0.6 ppmv. The detection limit was 0.016 ppmv, which is lower than the maximum exposure concentrations recommended by both the World Health Organization (WHO) and the Occupational Safety and Health Administration (OSHA). The optical sensor was found to have good reproducibility, with a relative standard deviation of 2.3 and 1.7% at 0.08 and 0.25 ppmv, respectively. The sensor can operate at room temperature and environmental humidity, 25 °C, and 50% RH, respectively. In addition, a study of interferents (acetaldehyde, toluene, methanol, ethyl acetate, acetone, acetic acid, carbon dioxide and ammonia) showed high selectivity for formaldehyde, which indicates that this membrane is a simple, fast, and economical alternative for quantifying the concentration of formaldehyde in different environments.

Sensitivity of Freshwater Australian Bass (Macquaria novemaculeata) and Silver Perch (Bidyanus bidyanus) to Waterborne Antimony: Exposure–Dose–Response Characteristics and Ion Homeostasis

We conducted acute toxicity studies using semi-static protocols to examine the lethal responses of Australian bass and silver perch exposed to antimony (Sb) oxidation states in Sb(III) (10.5-30.5mg L-1) and Sb(V) (95.9-258.7mg L-1). Bioavailability and the effects of Sb on body ion regulation (Na, Ca, Mg, and K) were also investigated. Antimony species-specific effects were observed with exposure to both Sb oxidation states. Median lethal concentrations (LC50s) for Sb(III) were 13.6 and 18mg L-1 for Australian bass and silver perch, respectively, and the LC50 for Sb(V) in Australian bass was 165.3mg L-1. The LC50 could not be calculated for silver perch exposed to Sb(V) as the maximum exposure concentrations produced 40% mortality but a larger-than value of > 258.7mg L-1 was estimated. Relative median potency values derived from the LC50s were 0.1 Sb(III) and 12.2 and 16.6 Sb(V) for Australian bass and silver perch, respectively, demonstrating greater toxicity of Sb(III) to both fish species. Antimony uptake in fish was observed. Median critical body residue (CBR50) values of 77.7 and 26.6mgkg-1 for Sb(III) were estimated for Australian bass and silver perch, respectively, and 628.1mgkg-1 for Sb(V) in Australian bass. Bioconcentration factors (BCFs) for both Sb(III) and Sb(V) did not change with exposure but the greater BCFs for fish exposed to Sb(III) indicate that it is more bioavailable than Sb(V) in acute exposure. No effects on whole-body Na, Ca, Mg, or K ions were observed with fish exposure to either Sb species.

Investigation on occupational hazards in 20 automobile manufacturing enterprises in Shandong Province

Objective: To investigate the current situation of occupational hazards in automobile manufacturing enterprises in Shandong Province. Methods: From February to May 2019, the convenience sampling method was adopted to conduct on-site occupational health surveys with 20 automobile manufacturing enterprises in Shandong Province as the survey subjects, to detect the occupational hazard factors in the workplaces and individual exposure levels, and to analyze the occupational health check results of operators. Results: There were 13 small-sized, 4 medium-sized and 3 large-sized enterprises among the 20 automobile manufacturing enterprises. The detection results of benzene and toluene in the workplaces met the occupational exposure limits, and the detection results of welding fumes, manganese and its compounds, and xylene exceed the occupational exposure limits. The maximum short-term exposure concentration (C(STE)) of welding fume in the air of workplaces was 24.23 mg/m(3), and the over-standard rate was 11.0% (16/146) . The maximum time-weighted average concentration (C(TWA)) of welding fume of operators is 10.60 mg/m(3), and the over-standard rate was 11.0% (8/73) . The maximum C(STE) of manganese and its compounds in the air of workplaces was 0.879 mg/m(3), and the of manganese and its compounds of operators was 0.175 mg/m(3), and the over-standard rate was 5.7% (4/70) . The maximum xylene C(STE) in the air of workplaces was 230.00 mg/m(3), and the over-standard rate was 3.9% (2/51) . The maximum xylene C(TWA) of operators was 70.40 mg/m(3), the over-standard rate was 3.6% (1/28) . Among the 4775 workers exposed to occupational hazards, 38 (0.80%) were suspected of electric welder's pneumoconiosis, 27 (0.57%) were suspected of manganese poisoning and 31 (0.65%) were suspected of chronic low-concentration benzene and benzene series poisoning. The detection rates of suspected occupational diseases among workers in small and medium-sized enterprises were relatively high, 2.86% (30/1048) and 4.51% (51/1132) respectively. There was a statistically significant difference in the detection rates of suspected occupational diseases among the operators of different scale automobile manufacturers (P<0.05) . Conclusion: The exposure levels of electric welding fumes, manganese and its compounds in welding jobs and xylene exposure levels in spray painting jobsin Shandong Province's automobile manufacturing enterprises are more serious. The supervision and management of occupational hygiene should be strengthened, the working environment should be improved, and the health of welding and painting workers should be protected.

Exposure to particulate matter in different private commuting modes in Salem, India

In our modern world, peoples are spending more time inside the vehicles in urban areas. This study assessed one of the critical pollutant of particulate matter PM10 (aerodynamic size ≤ 10 μm) in six private vehicles: hatchback car, sedan car, sports utility vehicle (SUV) car, multi utility vehicle (MUV) van, auto rickshaw, and motorcycle. PM pollutant in car and van transport modes evaluated under four different ventilation settings (air-conditioning (AC) ON/OFF; windows closed/open). In addition, air temperature (T) and relative humidity (RH) also assessed in six vehicles. The maximum PM exposure concentration was recorded in an auto-rickshaw, which is 4.28 times higher than the national pollution criteria. PM concentration lowered to 3.73, 1.94, and 1.53 timesin hatchback, sedan and SUV transport modes, respectively while altering ventilation condition from windows open to windows closed (AC ON) settings. There is no statistical significant difference (p > 0.05) between the transport modes of auto rickshaw-SUV, motorcycle-MUV, and motorcycle-sedan. All PM, T and RH parameters were correlated in car (AC ON) and auto-rickshaw transports.

Exposure to particulate matter and risk of amyotrophic lateral sclerosis: A case-control study in Northern Italy

Background: Amyotrophic lateral sclerosis (ALS) is progressive neurodegenerative disease with still unknown etiology. Role of occupational and environmental risk factors has been investigated, including outdoor air pollutants, which have been recently associated to an excess disease risk. We carried out a case-control study in order to assess if environmental exposure to particulate matter ≤10 µm (PM10) may increase ALS risk. Methods: We recruited patients referred to the Modena Neurology Unit between 1994-2015 and controls from the Modena province population. Using a validated geographical information system-based dispersion model, we geocoded subjects’ addresses of residence at the time of diagnosis and we estimated outdoor air PM10 concentrations for each subjects. We computed odds ratio (OR) and 95% confidence interval (CI) of ALS according to increasing PM10 exposure, using an unconditional logistic regression model age- and sex-adjusted. Results: For the 132 study participants (52 cases/80 controls), mean of annual average and maximum PM10 concentrations were 5.2 and 38.6µg/m3, respectively. Using fixed cutpoints at 5, 10 and 20 of average annual PM10 concentrations, compared with subjects &lt;5µg/m3, we did not find evidence for an excess ALS risk associated with PM10 exposure, since OR was 0.87 (95% CI 0.39-1.96), 0.94 (0.24-3.70), and 0.87 (0.05-15.01) at 5-10, 10-20 and ≥20µg/m3, respectively. Using maximum annual PM10 concentrations, we found an excess ALS risk for subjects exposed at 10-20µg/m3 (OR=4.27, 0.69-26.51) compared with exposure below 10µg/m3, although the risk tended to decrease at higher PM10 concentrations, with OR of 1.49 (0.39-5.75) at 20-50, and 1.16 (0.98-4.82) at ≥50µg/m3. Conclusions: Our findings do not suggest that PM10 exposure is associated with ALS risk. However, some evidence of an increased risk associated with maximum annual exposure concentrations, although statistically imprecise, suggests the need of further investigations, also considering the high concentrations of particulate matter characterizing Northern Italy.

Effect of modes of transportation on commuters' exposure to fine particulate matter (PM2.5) and nitrogen dioxide (NO2) in Chennai, India

Daily commuting increases level of contaminants inhaled by urban community and it is influenced by mode and time of commuting. In this study, the commuters’ exposure to ambient particulate matter (PM2.5) and nitrogen dioxide (NO2) was assessed during three modes of travel in six different road stretches of Chennai. The mean distance of road stretches was 25 km and the exposure to pollutants was assessed during peak hours and off-peak hours. The average travel duration was in the range of 39 to 91 min in motorbike, 83 to 140 min in car and 110 to 161 min in bus. Though there was variation on exposure to concentration in modes of transportation, the maximum exposure concentration of PM2.5 was observed as 709 μg/m&lt;sup&gt;3&lt;/sup&gt; in bus and the minimum exposure concentration was 29 μg/m&lt;sup&gt;3&lt;/sup&gt; in closed car. Similarly, the maximum exposure concentration of NO2 was observed to be 312 μg/m&lt;sup&gt;3&lt;/sup&gt; in bus and the minimum exposure concentration was 21 μg/m&lt;sup&gt;3&lt;/sup&gt; in car. The concentration of elements in PM2.5 was in the order of Si &gt; Na &gt; Ca &gt; Al ≥ K &gt; S ≥ Cd, with Si and Cd concentration as 60% and &lt; 1% of the PM2.5 concentration.

Molecular Evaluation of Impacted Reproductive Physiology in Fathead Minnow Testes Provides Mechanistic Insights into Insensitive Munitions Toxicology

Previous toxicological investigations of the insensitive munition (IM), 3-nitro-1,2,4-triazol-5-one (NTO), demonstrated histopathological and physiological impacts in mammalian testes. The implications of these findings for fish was unknown, therefore we investigated the effects of chronic (21 day) exposures to NTO and an NTO-containing IM formulation called IMX-101 (composed of 2,4-dinitroanisole (DNAN), nitroguanidine (NQ), and NTO) in adult male fathead minnows to assess if impacts on testes were conserved. The NTO exposure caused no significant mortality through the maximum exposure concentration (720 mg/L, measured), however NTO elicited testicular impacts causing significant asynchrony in spermatogenesis and necrosis in secondary spermatocytes at the two highest exposure concentrations (383 mg/L and 720 mg/L) and testicular degeneration at the highest exposure. Microarray-based transcriptomics analysis identified significant enrichment of steroid metabolism pathways and mTORC-signal control of spermatogonia differentiation in NTO exposures each having logical connections to observed asynchronous spermatogenesis. Additionally, NTO impaired transcriptional expression for genes supporting sperm structural and flagellar development including sperm-associated antigen 6 (Spag6). These functional transcriptomic responses are hypothesized contributors to impacted reproductive physiology in NTO exposures that ultimately lead to reductions in spermatozoa. In contrast to NTO, the IMX-101 formulation elicited significant mortality at the two highest exposure concentrations of 25.2 and 50.9 mg/L (DNAN nominal + NTO measured + NQ measured). Unlike NTO and NQ, the DNAN component of the IMX-101 formulation underwent significant transformation in the 21d exposure. From previous investigations, neither NTO nor NQ caused mortality in fish at >1000 mg/L suggesting that mortality in the present study arose from DNAN / DNAN-attributable transformation products. The 12.6 mg/L IMX-101 exposure caused significant sublethal impacts on testes including sperm necrosis, interstitial fibrosis, and Sertoli-like cell hyperplasia. Transcriptional profiles for IMX-101 indicated significant enrichment on multiple signaling pathways supporting spermatogenesis, mitosis / meiosis, and flagellar structure, all logically connected to observed sperm necrosis. Additionally, pronounced transcriptional increases within the PPARα-RXRα pathway, a known DNAN target, has been hypothesized to correspond to Sertoli cell hyperplasia, presumably as a compensatory response to fulfill the nurse-function of Sertoli cells during spermatogenesis. Overall, the transcriptional results indicated unique molecular responses for NTO and IMX-101. Regarding chemical hazard, NTO impacted testes and impaired spermatogenesis, but at high exposure concentrations (≥ 192 mg/L), whereas the IMX-101 formulation, elicited mortality and impacts on reproductive physiology likely caused by DNAN and its transformation products present at concentrations well below the NTO-component concentration within the IMX-101 mixture formulation.

Smartphone-Based Microfluidic Colorimetric Sensor for Gaseous Formaldehyde Determination with High Sensitivity and Selectivity.

Formaldehyde is one of the most dangerous air pollutants, which can cause sick building syndrome. Thus, it is very crucial to precisely determine formaldehyde with a low cost and simple operation. In this paper, a smartphone-based microfluidic colorimetric sensor is devised for gaseous formaldehyde determination with high sensitivity and selectivity. Specifically, a novel microfluidic chip is proposed based on the 4-aminohydrazine-5-mercapto-1,2,4-triazole (AHMT) method to determine formaldehyde; the chip consists of two reagent reservoirs, one reaction reservoir and a mixing column. In this design to prevent the fluid from flowing out while letting the gas molecule in, a hydrophobic porous poly tetra fluoroethylene (PTFE) membrane is put on the top of the reaction reservoir. Using the microfluidic chip sensor, a smartphone-based formaldehyde determination system is developed, which makes the measuring process automated and simple. As per the experiment results, the limit-of-detection (LOD) of the system is as low as 0.01 ppm, which is much lower than the maximum exposure concentration (0.08 ppm) recommended by the World Health Organization (WHO). Moreover, the sensor is hardly affected by acetaldehyde, volatile organic compounds (VOCs) or acidic-alkaline, which shows great selectivity. Finally, the performance of the proposed sensor is verified by using it for the determination of formaldehyde in a newly decorated house.

An automated screening method for detecting compounds with goitrogenic activity using transgenic zebrafish embryos.

The knowledge on environmentally relevant chemicals that may interfere with thyroid signaling is scarce. Here, we present a method for the screening of goitrogens, compounds that disrupt the thyroid gland function, based on the automatic orientation of zebrafish in a glass capillary and a subsequent imaging of reporter gene fluorescence in the thyroid gland of embryos of the transgenic zebrafish line tg(tg:mCherry). The tg(tg:mCherry) reporter gene indicates a compensatory upregulation of thyroglobulin, the thyroid hormone precursor, in response to inhibition of thyroid hormone synthesis. Fish embryos were exposed to a negative control compound (3,4-dichloroaniline), or a concentration series of known goitrogenic compounds (resorcinol, methimazole, potassium perchlorate, 6-propyl-2-thiouracil, ethylenethiourea, phloroglucinol, pyrazole) with maximum exposure concentration selected based on mortality and/or solubility. Exposure to 3,4-dichloroaniline decreased the fluorescence signal. All goitrogenic compounds exhibited clear concentration-dependent inductions of reporter fluorescence 1.4 to 2.6 fold above control levels. Concentration-response modelling was used to calculate goitrogenic potencies based on EC50 values. The new automated method offers an efficient screening approach for goitrogenic activity.

Personal Exposure to PM2.5 in the Megacity of Mexico: A Multi-Mode Transport Study

Recurrent personal exposure to ambient PM2.5 is associated with adverse human health effects, in particular on the respiratory and cardiovascular systems. Here, we present an assessment of personal exposure and inhalation of PM2.5 for five modes of transport (walking, cycling, public bus (trolleybus and diesel bus), conventional car (CC) and hybrid-electric car (HEC)) and two routes of similar distance, along a major road in the Mexico City metropolitan area (MCMA). Arithmetic average exposure concentrations ranged from 16.5 ± 6.5 µg m−3 for walking to 81.7 ± 9.1 µg m−3 for cycling (henceforth shown as average ±1 SD), with no significant differences with geometric averages. The maximum exposure concentration of 110.9 µg m−3 was observed for the conventional car. The highest exposure concentrations depended on route and the mode of transport, being observed for cycling and walking. The PM2.5 measurements showed large spatial heterogeneity in the exposure levels for walking and cycling, while public buses and private transport showed less spatial heterogeneity. The greatest peaks in PM2.5 coincided with 4-way intersections for all modes of transport, being positively influenced by traffic density. The mass of PM2.5 inhaled depended mostly on the mode of transport, and ranged between 1.0 ± 0.3 and 30.1 ± 14.2 µg km−1 for the HEC and bicycle, respectively. Local area PM2.5 increments identified as ‘residuals’ after subtraction of data recorded at the closest fixed monitoring site from exposure concentrations along the studied road suggested that inhalation for bicycle and diesel buses is strongly influenced by vehicular emissions. Residuals estimated for the trolleybus, CC and HEC confirmed a lower inhalation than for the other modes of transport evaluated due to protection by the cabin.

Field-based method for evaluating the annual maximum specific conductivity tolerated by freshwater invertebrates

Most water quality criteria are based on laboratory toxicity tests and usually include chronic and acute magnitudes. Field-based criteria are typically based on long-term or continuous exposures, so they are chronic. Biological responses of quantified, short-term aqueous exposures are seldom documented in the field. However, acute values may be derived by estimating an upper limit using temporal variance and chronic values. This method estimates an upper limit from the variance of pollutant measurements from stream locations that attain the chronic criterion. The formula for deriving a 90th centile of a standard normal distribution is used to identify the upper limit, a criterion maximum exposure concentration (CMEC). The calculated CMEC is interpreted as a maximum exposure that 95% of organisms may tolerate if the chronic exposure is not exceeded. The methods of deriving chronic and acute criteria are illustrated with specific conductivity in a mountainous area in the eastern United States. The biological relevance of the CMEC was assessed using the maximum annual exposure during the life cycle of the most salt-intolerant genera. The method using the chronic criterion and the variance of water chemistry data is practical, whereas frequently collecting and analyzing paired biological and chemical samples at numerous sites is impractical and may give misleading results due to lags in biological response. This method can be used anywhere with sufficient data to estimate the temporal variability and may be applicable for field-based criteria other than the specific conductivity criteria illustrated here.

PAHs exposure and occupational health risk assessment of workers in coal tar pitch factory

Objective: To Investigation of industrial sites involving coal tar pitch to detect PAHs in the occupational environment and to assess their occupational health risks to workers. Methods: Taking coal tar pitch enterprises as the research object, and making the occupational health field investigation and inspection. Detecting the 16 PAHs in the samples by high performance liquid chromatography (HPLC) , analyze the PAHs exposed dose of the workers in the place, and using cumulative toxic equivalent quantity method, loss of life expectancy method and carcinogenic risk factor method to assessment worker's occupational health risk. Results: In the 15 posts involved, Some workers' exposed to the total concentration of PAHs is higher than others, the maximum exposure concentration is 1931.45ng/m3. There are different hazard risk levels in different working post due to different processes.The lifetime risk of workers is significantly higher than the acceptable range. Some workers has higher carcinogenic risk and workers' life expectancy loss is up to 1033.95 hours. Conclusion: Part of the coal tar pitch workers exposed to higher concentrations of PAHs, and beyond the occupational exposure limits.And there is a high occupational health risk due to high exposure to PAHs.

The Emperor's Old Clothes: An Inconvenient Truth About Currently Accepted Vapor Intrusion Assessment Methods

The Emperor's Old Clothes: An Inconvenient Truth About Currently Accepted Vapor Intrusion Assessment Methods

Chemical exposure levels in printing workers with cholangiocarcinoma (second report).

In several Japanese printing plants, printing workers have suffered from cholangiocarcinoma. 1,2-dichloropropane (1,2-DCP) is considered to be a causative agent, and whether or not other chemicals also contribute to the development of this disease has not been conclusively determined. This study aimed to identify the chemicals used by seven printing workers who developed cholangiocarcinoma, as well as to estimate the levels of chemical exposure among them. Information was obtained from the Ministry of Health, Labour and Welfare, Japan, to identify chemicals used by printing workers who developed cholangiocarcinoma and to estimate chemical exposure concentrations. Working environment concentrations of the chemicals in the printing rooms were estimated using a well-mixed model, and exposure concentrations during the ink removal operation were estimated using a near-field and far-field model. Shift time-weighted averages of exposure concentrations were also calculated. Four of the seven printing workers were exposed to both 1,2-DCP and dichloromethane (DCM). The estimated maximum exposure concentrations for each of the four workers were 230 to 420 ppm for 1,2-DCP and 58 to 720 ppm for DCM, and the estimated shift average exposure concentrations were 0 to 210 ppm for 1,2-DCP and 15 to 270 ppm for DCM. The remaining three workers were exposed to DCM but not 1,2-DCP. The estimated maximum exposure concentrations of DCM for each of the three workers were 600 to 1,300 ppm, and the estimated shift average exposure concentrations were 84 to 440 ppm. Our findings suggest that DCM may contribute to the development of cholangiocarcinoma in humans.

Ecological risk assessment of the antibiotic enrofloxacin applied to Pangasius catfish farms in the Mekong Delta, Vietnam

Antibiotics applied in aquaculture production may be released into the environment and contribute to the deterioration of surrounding aquatic ecosystems. In the present study, we assessed the ecological risks posed by the use of the antibiotic enrofloxacin (ENR), and its main metabolite ciprofloxacin (CIP), in a Pangasius catfish farm in the Mekong Delta region, Vietnam. Water and sediment samples were collected in a stream receiving effluents from a Pangasius catfish farm that had applied ENR. The toxicity of ENR and CIP was assessed on three tropical aquatic species: the green-algae Chlorella sp. (72h – growth inhibition test), the micro-invertebrate Moina macrocopa (48h – immobilization test), and the Nile tilapia (Oreochromis niloticus). The toxic effects on O. niloticus were evaluated by measuring the cholinesterase (ChE) and catalase (CAT) activities in the fish brain and muscles, respectively, and by considering feed exposure and water exposure separately. Ecological risks were assessed by comparing maximum exposure concentrations with predicted no effect concentrations for cyanobacteria, green algae, invertebrates and fish derived with available toxicity data. The results of this study showed that maximum antibiotic concentrations in Pangasius catfish farm effluents were 0.68μgL−1 for ENR and 0.25μgL−1 for CIP (dissolved water concentrations). Antibiotics accumulated in sediments down-stream the effluent discharge point at concentrations up to 2590μgkg−1 d.w. and 592μgkg−1 d.w. for ENR and CIP, respectively. The calculated EC50 values for ENR and CIP were 111000 and 23000μgL−1 for Chlorella sp., and 69000 and 71000μgL−1 for M. macrocopa, respectively. Significant effects on the ChE and CAT enzymatic activities of O. niloticus were observed at 5gkg−1 feed and 400–50000μgL−1, for both antibiotics. The results of the ecological risk assessment performed in this study indicated only minor risks for cyanobacteria communities, suggesting that residual concentrations of ENR and CIP after medication are not likely to result in severe toxic effects on exposed aquatic ecosystems. However, more studies should be performed by considering other antibiotic treatments used in Pangasius catfish production and the potential ecotoxicological effects of relevant antibiotic mixtures on sediment communities.

씨앗발아 및 발아지수에 근거한 나노입자 독성평가

나노물질은 다양한 분야에 널리 사용되고 있다. 본 연구에서는 Lactuca(상추)와 Raphanus(알타리무) 씨앗의 발아와발아지수에 금속산화물 나노입자(CuO, NiO, Fe₂O₃, CO₃O₄, TiO₂, ZnO)가 미치는 영향을 조사하였다. 용액상 노출에서 CuO가가장 큰 영향을 나타내었으며, 발아와 발아지수의 EC50는 각 0.46 mg/L와 0.37%로 조사되었다. 씨앗 이용 식물독성 측정에서상추가 알타리무보다 나노입자 노출에 대해 더욱 민감한 반응을 나타내었다. 일반적으로 나노입자의 씨앗발아와 발아지수에근거한 영향은 다음의 순서로 조사되었다: CuO > ZnO>NiO > TiO₂, Fe₂O₃, CO₃O₄. 특히 TiO₂, Fe₂O₃와 CO₃O₄는 최대 노출 농도 1,000 mg/L 농도에서도 뚜렷한 영향을 나타내지 않았다.

Assessment of selection and resistance risk for demethylation inhibitor fungicides in Aspergillus fumigatus in agriculture and medicine: a critical review

An increasing number of publications have claimed that demethylation inhibitor (DMI) fungicides are confronted with resistance development in the fungus Aspergillus fumigatus and that the origin of resistant isolates may also be outside the medical area. For resistance risk assessment and sourcing the origin of DMI resistance, the primary exposure events ofA. fumigatus with DMI treatments have been analysed case by case, resulting in the pathogen exposure risk (PER). The calculated maximum exposure concentrations (MEC) are highest during medical treatments (human and veterinary), certain fruit and seed treatments and wood preservation, and are much lower for crop protection applications. Most agricultural DMIs are intrinsically ∼10-100 times less active than medical DMIs for A. fumigatus control and potential resistance selection. However, imazalil is used in agriculture and veterinary medicine (as enilconazole) expressing strong intrinsic activity against A. fumigatus. The majority of mutations in the target gene, cyp51, of DMI-resistant isolates are different in A. fumigatus(e.g. TR34/L98H) in comparison with plant pathogens (e.g. A379G, I381V). The assumed selection risk, ASR (MEC × PER) for resistance evolution to DMIs in A. fumigatus is estimated to be highest for human and veterinary applications. However, environmental origin of DMI-resistant spores from certain sites cannot be ruled out.

Proposal for applying a component-based mixture approach for ecotoxicological assessment of fracturing fluids

Hydraulic fracturing is increasingly being used to produce gas from unconventional resource sites for energy supply. Therefore, concerns about risks of this technology related to human health and the environment have to be addressed. Among the major issues is the potential contamination of surrounding water systems by chemical additives used in fracturing fluids. In this study, the ecotoxicological hazards of fracturing fluids, both, their individual components (chemicals) as well as their mixtures (product) were assessed using a component-based mixture approach. For five exemplary fracturing fluids, 40–90 wt% of the contained substances could unambiguously be defined in their chemical identity. The concentrations used in the applied fluid mixture were considered as (maximum) exposure concentrations. For components with mass fractions between 10 and 74 wt%, the effect concentrations for acute and chronic toxicity of fish, daphnia and algae were retrieved from experimental databases and through predictive modeling. The hazard indices calculated from the ratio of exposure to effect concentration were >1 for all fracturing fluids, using different scenarios. This indicated a hazard from the undiluted fracturing fluids. The assessment framework presented in this study allows for dealing with data gaps and uncertainties in a tiered fashion and in particular accommodates for combined effects resulting from chemical mixtures. It might be employed for ecotoxicological risk assessment of products containing chemical mixtures and optimization of their environmental performance.

Synergistic toxicity of Macondo crude oil and dispersant Corexit 9500A® to the Brachionus plicatilis species complex (Rotifera)

Using the marine rotifer Brachionus plicatilis acute toxicity tests, we estimated the toxicity of Corexit 9500A®, propylene glycol, and Macondo oil. Ratios of 1:10, 1:50 and 1:130 for Corexit 9500A®:Macondo oil mixture represent: maximum exposure concentrations, recommended ratios for deploying Corexit (1:10–1:50), 1:130 the actual dispersant:oil ratio used in the Deep Water Horizon spill. Corexit 9500A® and oil are similar in their toxicity. However, when Corexit 9500A® and oil are mixed, toxicity to B. manjavacas increases up to 52-fold. Extrapolating these results to the oil released by the Macondo well, suggests underestimation of increased toxicity from Corexit application. We found small differences in sensitivity among species of the B. plicatilis species complex, likely reflecting phylogenetic similarity. Just 2.6% of the water-accommodated fraction of oil inhibited rotifer cyst hatching by 50%, an ecologically significant result because rotifer cyst in sediments are critical resources for the recolonization of populations each Spring.