Acute Exposure Assessment Research Articles

Acute exposure and biomarkers assessment in rainbow trout exposed to selected pharmaceuticals

Pharmaceuticals released from municipal effluents discharges pose a risk to aquatic organisms. The toxicity of 5 pharmaceuticals with distinct therapeutic actions were assessed in rainbow trout: olanzapine (antipsychotic), erythromycin (antibiotic), mycophenoate (immunosuppression), pinaverium (anti-inflammatory) and trazodone (sedative). Juveniles were exposed to these drugs for 96 h at concentrations between 64 µg/L up to 40 mg/L to reach lethality. Survival was determined and a suite of biomarkers was analyzed for drug biotransformation, oxidative stress/damage and metabolic activity at sublethal concentrations. The data revealed the following toxicity: olanzapine >trazodone>mycophenolate>pinaverium∼erythromycin based on mortality. The data also revealed that toxicity was associated to mass, pKa and hydrophobicity and the following sublethal effects: GST, LPO and DNA strand breaks. Pharmaceuticals with lower molecular weight, physiological pKa, moderate hydrophobicity, low biotransformation and DNA strand breaks were generally more toxic to fish. However, this should be considered as a general guide in identifying toxic pharmaceuticals in non-target organisms.

Contamination Status and Risk Assessment of Paralytic Shellfish Toxins in Shellfish along the Coastal Areas of China.

Paralytic shellfish toxins (PSTs) are widely distributed in shellfish along the coast of China, causing a serious threat to consumer health; however, there is still a lack of large-scale systematic investigations and risk assessments. Herein, 641 shellfish samples were collected from March to November 2020, and the PSTs' toxicity was detected via liquid chromatography-tandem mass spectrometry. Furthermore, the contamination status and potential dietary risks of PSTs were discussed. PSTs were detected in 241 shellfish samples with a detection rate of 37.60%. The average PST toxicities in mussels and ark shells were considerably higher than those in other shellfish. The PSTs mainly included N-sulfonylcarbamoyl toxins (class C) and carbamoyl toxins (class GTX), and the highest PST toxicity was 546.09 μg STX eq. kg-1. The PST toxicity in spring was significantly higher than those in summer and autumn (p < 0.05). Hebei Province had the highest average PST toxicity in spring. An acute exposure assessment showed that consumers in Hebei Province had a higher dietary risk, with mussels posing a significantly higher dietary risk to consumers. This research provides reference for the green and sustainable development of the shellfish industry and the establishment of a shellfish toxin prevention and control system.

Contamination Status and Acute Dietary Exposure Assessment of Paralytic Shellfish Toxins in Shellfish in the Dalian Area of the Yellow-Bohai Sea, China

The Yellow-Bohai Sea is an important semi-enclosed continental shelf marginal seas with an intensive aquaculture industry in China. The current study analyzed the contamination status and the time variations of paralytic shellfish toxins (PSTs) in shellfish between 2019 and 2020 from the Yellow-Bohai Sea in the Dalian area and estimated the acute health risks to consumers in China. A total of 199 shellfish samples (including 34 Pacific oysters, 25 Mediterranean blue mussels, 34 Manila clams, 36 bay scallops, 34 veined rapa whelks and 36 bloody clams) were analyzed from four representative aquaculture zones around the Yellow-Bohai Sea in Dalian. Among the samples, scallops and blood clams were the shellfish species with the highest detection rate of PSTs (94.4%), and the highest level of PSTs was detected in scallops with 3953.5 μg STX.2HCl eq./kg (μg STX.2HCL equivalents per kg shellfish tissue), followed by blood clams with 993.4 μg STX.2HCl eq./kg. The contents of PSTs in shellfish showed a time variation trend, and autumn was the season of concern for PST contamination in Dalian. For general Chinese consumers, the probability of acute health risks to shellfish consumers from dietary exposure to PSTs was around 13%. For typical consumers in coastal areas of China, especially those with higher shellfish intake, there was an acute health risk associated with exposure to PSTs through shellfish consumption during the occurrence of harmful algal blooms. It is suggested that the government continue to strengthen the monitoring of the source of PSTs and the monitoring of harmful algal blooms and give reasonable advice on shellfish consumption for consumers in coastal areas, such as not eating scallop viscera.

A study of the pesticide residues in rapeseeds in China: Levels, distribution and health risk assessment

The aim of this survey was to evaluate the residue levels, distribution and exposure risk of the 38 most commonly used pesticides in rapeseed samples collected from the main production areas in China over a two-year period. The sampling area covered 12 provinces, including Guizhou, Shaanxi, Yunnan, Hunan, Jiangxi, Sichuan, Chongqing, Anhui, Henan, Hubei, Zhejiang, and Jiangsu provinces. The pesticide residues were determined using a QuEChERS (Quick Easy Cheap Effective Rugged and Safe) method coupled with gas chromatography-tandem mass spectrometry and liquid chromatography-tandem mass spectrometry. 8.4% of the rapeseed samples contained pesticides with a residue level ranging from 0.001 to 0.634 mg/kg. The detected analytes were imidacloprid, quizalofop-P-ethyl, thiamethoxam, paclobutrazol, prochloraz, tebuconazole, difenoconazole, s-metolachlor, carbofuran, and carbendazim. The concentrations of four analytes, including thiamethoxam, difenoconazole, carbendazim and prochloraz, exceeded the maximum residue level set by the Chinese government for rapeseed, with exceedance rates of 0.1%, 0.1%, 0.1%, and 1.1%, respectively. Based on the index of quality for residues (IqR) values, 91.6% of the total rapeseed samples had an IqR category of Excellent (IqR = 0). Only 1.5% of the tested samples were of inadequate quality. Furthermore, the assessment of chronic and acute exposure, as well as health risks associated with pesticide residues in rapeseed, was conducted for different age groups within the Chinese population, including adults (6–14 years), children (15–49 years), and the elderly (50–74 years). The results of this assessment indicated that pesticide residues in rapeseed cultivated in China are not expected to be of short- or long-term risks to the Chinese customers.

Risk assessment and spatial analysis of paralytic shellfish toxin (PST) concentrations and acute dietary exposure of commercially available shellfish in coastal areas in China

Paralytic shellfish toxins (PSTs) are produced by marine dinoflagellates and can be accumulated in filter feeding shellfish. In this study, we assessed acute dietary exposure to PSTs among residents of Chinese coastal provinces and cities, utilizing point and probabilistic estimates. Additionally, we performed global and local spatial autocorrelation analyses to evaluate PSTs contamination and dietary exposure levels in the coastal regions of China. The point estimate revealed that Hebei province exhibited the highest level of PSTs dietary exposure, measuring 39.57 μgSTXeq./kgbw. In all regions, except for Guangxi, Jiangsu, Shandong, and Shanghai, the ratio between acute dietary exposure and the acute reference dose (ARfD) exceeded 1. Probabilistic estimates indicated that P99.9 exceeded the ARfD value exclusively in Guangdong, Hainan, and Liaoning. In comparison, the point estimate was significantly higher than the P99.9 value of the probabilistic estimate. The spatial analysis results showed “low-high" aggregation of PSTs concentration and point estimate dietary exposure levels in Liaoning and Shandong, while probabilistic estimate dietary exposure level exhibited “low-high" aggregation in Guangxi. This implied the presence of regional variations in PSTs contamination and dietary exposure within the coastal regions of China, along with specific localized clustering features. Therefore, it is advisable to develop regionalized precision monitoring and dietary interventions to ensure the safety of shellfish consumption, particularly in response to the regional distribution characteristics of PSTs contamination and dietary exposure.

Assessing Acute and Chronic Risks of Human Exposure to Arsenic: A Cross-Sectional Study in Ethiopia Employing Body Biomarkers.

Arsenic, a widely recognized and highly toxic carcinogen, is regarded as one of the most hazardous metalloids globally. However, the precise assessment of acute and chronic human exposure to arsenic and its contributing factors remains unclear in Ethiopia. The primary goal of this study was to assess the levels of acute and chronic arsenic exposure, as well as the contributing factors, using urine and nail biomarkers. A community-based analytical cross-sectional study design was employed for this study. Agilent 7900 series inductively coupled plasma mass spectrometry was used to measure the concentrations of arsenic in urine and nail samples. We performed a multiple linear regression analysis to assess the relationships between multiple predictors and outcome variables. The concentration of arsenic in the urine samples ranged from undetectable (<0.01) to 126.13, with a mean and median concentration of 16.02 and 13.5 μg/L, respectively. However, the mean and median concentration of arsenic in the nails was 1.01, ranging from undetectable (<0.01 μg/g) to 2.54 μg/g. Furthermore, Pearson's correlation coefficient analysis showed a significant positive correlation between arsenic concentrations in urine and nail samples (r = 0.432, P < .001). Also, a positive correlation was observed between urinary (r = 0.21, P = .007) and nail (r = 0.14, P = .044) arsenic concentrations and the arsenic concentration in groundwater. Groundwater sources and smoking cigarettes were significantly associated with acute arsenic exposure. In contrast, groundwater sources, cigarette smoking, and the frequency of showers were significantly associated with chronic arsenic exposure. The study's findings unveiled the widespread occurrence of both acute and chronic arsenic exposure in the study area. Consequently, it is crucial to prioritize the residents in the study area and take further measures to prevent both acute and chronic arsenic exposure.

Consumption of Bivalve Shellfish in French Coastal Populations: Data for Acute and Chronic Exposure Assessment

Shellfish are a source of nutrients but are also a matter of concern in terms of food safety due to natural contaminants such as phycotoxins or anthropogenic contaminants including microbial agents and heavy metals. However, data related to consumption for each mollusk species are scarce and missing for appropriate exposure calculation. The objective of the study was to generate shellfish consumption data in the adult coastal population in France to assess exposure to health risks, the effects of determinants on the frequency of consumption and usual intake, and shellfish food risk perception. Our study, named the CONSOMER study, was carried out using an online survey in 2016 and 2017 and included a food frequency questionnaire. After validation, 2,479 individual questionnaires were available for statistical analysis. Our findings provide estimates of shellfish consumption frequency, portion sizes, weekly intake in g/week, and g/week/body weight that can be used for acute and chronic exposure calculations. For the acute risk, the 97.5th percentile of the portion size was found to be around 290 g for the adult coastal population. For chronic exposure, recreational shellfish harvesting activities were associated with higher weekly intakes. A non-negligible part of this subpopulation is not aware of food safety recommendations concerning harvesting areas. Results for shellfish harvester consumption in particular are consistent with other available data. Exposure calculations and safety recommendations should target shellfish harvesters.

Targeted risk assessment for prochloraz.

In accordance with Article 43 of Regulation (EC) No 396/2005, the European Commission requested EFSA to prepare a statement with a targeted risk assessment for prochloraz. Based on the data available, EFSA performed an acute exposure assessment for EU consumers for the existing EU maximum residue levels (MRLs) based on codex maximum residue limits (CXLs) and identified possible risk for consumers for the CXLs on granate apples and papaya.

Determination of Biogenic Amines in Wine from Chinese Markets Using Ion Chromatography-Tandem Mass Spectrometry.

A method for the determination of nine biogenic amines (BAs) in wine was established using ion chromatography-tandem mass spectrometry (IC-MS/MS) without derivatization. BAs were separated by a cation exchange column (IonPac CG17, 50 mm × 4 mm, 7 µm) with a gradient aqueous formic acid elution. Good linearity was obtained for nine BAs with coefficients of determination (R2) > 0.9972 within the range of 0.01-50 mg/L. The limits of detection and quantification were within the ranges of 0.6-40 µg/L and 2.0-135 µg/L, respectively, with the exception of spermine (SPM). The recoveries were demonstrated within the range of 82.6-103.0%, with relative standard deviations (RSDs) of less than 4.2%. This simple method featuring excellent sensitivity and selectivity was suitable for the quantification of BAs in wines. The occurrence of BAs in 236 wine samples that are commercially available in China was determined. The BA levels in wines of different geographical origins varied significantly. The acute dietary exposure assessment of BAs was carried out by calculating the estimated short-term intake (ESTI) and comparing the acute reference dose (ARfD) specified by the European Food Safety Authority (EFSA). Results showed that the exposure to histamine (HIS) and tyramine (TYR) via the consumption of wines was much lower than the recommended ARfD level for healthy individuals. However, exposure could lead to symptoms in susceptible individuals. These results provided basic data regarding the occurrence and risk of BAs in wines for wine production, health guidance and consumer safety.

Risk Assessment and Hepatotoxicity of Acute Exposure to Chlorview (chlorpyrifos 40% E.C.) Via Oral and Inhalation Routes Using Animal Model

Aims: This research aimed to determine the Hepatotoxicity via oral and inhalation routes using animal model and its Risk assessment when exposed to Chlorview pesticide (Chlorpyrifos 40% E.C.).&#x0D; Study Design: The animals were divided into two groups for oral and inhalation routes of exposure. They were divided into 4 groups of 5 animals each for oral and 4 groups of 4 animals each for inhalation.&#x0D; Place and Duration of Study: This study was conducted in the Department of Biochemistry Laboratory University of Nigeria Nsukka.&#x0D; Methodology: The hepatotoxicity and risk assessment studies were carried out using a colorimetric assay and standard methods respectively.&#x0D; Results: Oral exposure to Chlorview led to a significant (p&lt;0.05) increase in the activity of AST, ALT, and ALP when compared to the control. The risk assessment studies showed oral subchronic toxicity at the dose of 15.5 mg/kg b.w when exposed to Chlorview with a bioaccumulation factor (BAF) of 2.50. The oral exposure recorded a hazard quotient (HQ) of 3.4 and a risk quotient (RQ) of 0.1, a risk presumption of acute restricted use. There was no accumulation of the pesticide or its derivative via the inhalation route rather a macroscopic deposition of fat on the liver identified as cholesterol was seen.&#x0D; Conclusion: This research suggests that exposure to Chlorview pesticide through oral and inhalation routes can pose a reasonable risk to human health.

Risk assessment related to the presence of benzalkonium chloride (BAC), didecyldimethyl ammonium chloride (DDAC) and chlorates in fish and fish products.

In compliance with Article 31 of Regulation (EC) No 178/2002, EFSA received a mandate from the European Commission to prepare a statement on the risk assessment related to the presence of benzalkonium chloride (mixture of alkylbenzyldimethylammonium chlorides with alkyl chain lengths of C8, C10, C12, C14, C16 and C18) (BAC), didecyldimethylammonium chloride (mixture of alkyl-quaternary ammonium salts with alkyl chain lengths of C8, C10 and C12) (DDAC) and chlorates in fish and fish products. Within EFSA's annual chemical data collection, EFSA collected monitoring data for the residues of BAC, DDAC and chlorates from EU Member States, Iceland and Norway performed a statistical evaluation, providing estimated residue values for each substance in/on fish and fish products, at the percentile appropriate for the number of the available samples. Based on the information collected, EFSA performed an acute and chronic exposure assessment for EU consumers for BAC, DDAC and chlorates at the lower-bound, medium-bound and upper-bound scenarios resulting from the consumption of fish and fish products. EFSA did not identify potential consumer health risks associated to residues of the substances found in fish and fish products.

Residue analysis and dietary risk assessment of thiamethoxam, flonicamid and their metabolites in cucumber under field conditions in China.

Thiamethoxam and flonicamid are two representative insecticides of neonicotinoids which are used to treat cucumber aphids, causing food safety and human health problems. A 60% thiamethoxam-flonicamid commercial mixture water dispersible granule (WDG) is being prepared for registering in China, so it is essential to investigate the residue levels of these neonicotinoids and their metabolites in cucumber and evaluate the dietary risks of these insecticides. We developed a modified quick, easy, cheap, effective, rugged and safe (QuEChERS) method combined with high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) for the simultaneous determination of thiamethoxam and its metabolite clothianidin, flonicamid and its metabolites 4-trifluoromethylnicotinic acid (TFNA), 4-trifluoromethilnicotinamide (TFNA-AM), 4-(trifluoromethyl) nicotinol glycine (TFNG) in cucumber. Method validation indicated good selectivity, linearity (r ≥ 0.9996), accuracy (recoveries of 80-101%), precision (relative standard deviations (RSD) ≤ 9.1%), sensitivity (limits of detection (LOD), 0.28-1.44 × 10-3mg/L; limits of quantification (LOQ), 0.01mg/kg) and minor matrix effect (ME) ( ≤|± 5%|). In the terminal residue trials under good agricultural practice (GAP) conditions, the residue levels of six analytes in cucumber samples were ˂0.01-0.215mg/kg after application trice with an interval of 7days based on pre-harvest interval (PHI) of 3days under the high recommended dosage of 54g active ingredient/ha (g a.i./ha). Relevant toxicological, residual chemistry parameters and dietary consumption of the residents were applied to assess the potential risk of dietary exposure. The chronic and acute dietary exposure assessment risk quotient (RQ) values were less than 1. The above results indicated that the potential dietary intake risk of this formulation was negligible to consumers.

Determination and dietary exposure assessment of 79 pesticide residues in Chinese onion (Allium fistulosum L.)

ABSTRACT Chinese onion is a common vegetable in daily diet, especially in Southwest China. We collected 184 samples from farm and market in Chongqing Municipality during 2020–2021 and established a multi-residue method for analysis of 79 pesticide residues on Chinese onion. Sixty-three of 184 samples were found pesticide resdues, accounting for 34.2%. A total of 31 pesticides were detected, and 6 pesticides in 11 samples have exceeded the Chinese MRLs, 5.98% of all samples. The chronic and acute dietary exposure assessment showed the %ADI and the %ARfD value were 0.005%–5.46% and 0.03%–297.95%, respectively. The %ARfD of most pesticides were acceptable except for cyhalothrin (297.95%, children; 140.17%, adults) and carbofuran (107.94%, children). The study indicated that pesticide residues on Chinese onion had different concentration levels which were low commonly. The establishment of MRLs for several pesticides (cyfluthrin, carbendazim, propamocarb) in Chinese onion is required for better estimation of dietary risk.

Refining acute human exposure assessment to pesticides in surface water: An integrated data-driven modeling approach

The substantial spatial and temporal variability of pesticides has led to large uncertainties when determining their peak aqueous concentrations. There is however a lack of large-scale studies dealing with accurate determination of annual maximum daily concentration (AMDC) across the landscape and over time based on the publicly available monitoring data. We developed a novel data-driven approach that firstly used time series modeling to generate AMDCs for qualified water monitoring sites in the conterminous U.S. With feature variables such as pesticide use and land cover compiled into the dataset, machine learning models using eXtreme Gradient Boosting (XGBoost) and Random Forest Regressor (RF) were then developed to estimate AMDCs in surface waters across the U.S. Both models exhibited significant predictability, while a hybrid model consisting of the average predictions by XGBoost and RF model had the highest prediction accuracy (mean absolute error (MAE): 1.23; R2: 0.61). The analysis of permutation variable importance indicated that pesticide use and drainage area were the two most important drivers. Partial dependence analysis revealed that pesticide use, precipitation, cultivated crop land cover and solubility exhibited concentration-promoting effects, whereas drainage area and molecular weight had concentration-demoting effects. Soil adsorption coefficient (Koc) showed nonmonotonic effects. The hybrid model was used to predict and map AMDCs of four example pesticides, including 2,4-dichlorophenoxyacetic acid (2,4-D), atrazine, glyphosate and imidacloprid during 2016–2019 at national scale. The predictive capability was validated using independent monitoring datasets. The fully evaluated approach significantly reduced the uncertainties in modeling annual peak concentrations and served as a valuable solution for conducting geographically oriented, highly refined exposure assessments for pesticides.

Determination, residue analysis and risk assessment of thiacloprid and spirotetramat in cowpeas under field conditions

The dissipation and residue levels of thiacloprid, spirotetramat and its four metabolites residues in cowpeas were investigated under field conditions. The QuEChERS technique with high-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) was used to detect thiacloprid, spirotetramat and its four metabolites residues content in cowpeas. The recoveries were 81.3–95.1% at a spike level of 0.005–0.5 mg/kg, the relative standard deviations (RSDs) were 2.1–9.5%. The dissipation kinetics data showed that thiacloprid and spirotetramat in cowpeas were degraded with the half-lives of 1.14–1.54 days and 1.25–2.79 days. The terminal residues of thiacloprid and spirotetramat were 0.0255–0.4570 mg kg−1 and 0.0314–0.3070 mg kg−1 after application 2 times with a pre-harvest interval (PHI) of 3 days under the designed dosages. The chronic and acute dietary exposure assessment risk quotient (RQ) values of thiacloprid in cowpeas for different consumers were 2.44–4.41% and 8.72–15.78%, respectively, and those of spirotetramat were 1.03–1.87% and 0.18–0.32%, respectively, all of the RQ values were lower than 100%. The dietary risk of thiacloprid through cowpeas to consumers was higher than spirotetramat. The results from this study are important reference for Chinese governments to develop criteria for the safe and rational use of thiacloprid and spirotetramat, setting maximum residue levels (MRLs), monitoring the quality safety of agricultural products and protecting consumer health.

Multi-residue method validation and safety evaluation of pesticide residues in seed spices cumin (Cuminum cyminum) and coriander (Coriandrum sativum) by gas chromatography tandem mass spectrometry (GC–MS/MS)

The manuscript reports comprehensive multi-residue determination of 215 pesticides in two commercially important Indian spices, Cumin (Cuminum cyminum) and Coriander (Coriandrum sativum) by GC–MS/MS analysis. The proposed method involved liquid–liquid extraction with acetonitrile, d-SPE clean-up and final reconstitution of extract in ethyl acetate. d-SPE clean-up with PSA and C18 minimized the matrix effects by 40 and 16%, respectively. Reconstitution of final extract reduced the non-volatile matrix co-extractives by 36–40%. The method was validated as per SANTE/12682/2019 and recoveries at 10, 25 and 50 μg kg−1 were within 70–120% with RSD ≤ 20%. A fit for purpose method LOQ of 10 μgkg−1 was achieved for 85% of analytes. The method was successfully applied for comprehensive screening of cumin and coriander market samples. The calculated TMDI for acute and chronic exposure assessment were less than calculated MPI in respective matrices and therefore did not cause any adverse effect to consumers.

Dietary exposure assessment of paralytic shellfish toxins through shellfish consumption in Shenzhen population, China.

Paralytic shellfish toxins (PSTs) produced by certain marine dinoflagellates accumulate in filter-feeding marine bivalves. We used LC-MS/MS to detect and quantify 13 PSTs in 188 shellfish samples of 14 species collected from Shenzhen city's Buji seafood wholesale market from March 2019 to February 2020. Twenty-six of 188 shellfish samples (13.8%) were PSTs detectable. Within 14 species, 10 out of 34 noble clam Chlamys nobilis samples contain detectable PSTs with the highest detection rate 29.4%. Seven out of 17 samples from Nan'ao island contained detectable PSTs with the highest detection rate 41.2% among 11 origins. Samples containing PSTs were concentrated in spring and winter, with the highest levels in March>December>January. Among PSTs detected, C1 was dominant. Acute dietary exposure assessment for Shenzhen residents were based on mean adult body weight, 99th percentile daily shellfish consumption of Shenzhen food consumption survey 2008 and maximum PSTs concentration for each shellfish species. The outcome for Chlamys nobilis was 2.4~3.7-fold higher than recommended ARfDs. Mean PSTs concentration, P99, and mean shellfish consumption were used to assess chronic dietary exposure. The results were lower than recommended ARfDs. In conclusion, residents in Shenzhen are at risk for acute PSTs poisoning, while relatively safe from chronic PSTs exposure.

Multivariate Optimization of an SPME Technique for GC-MS Analysis of Urinary BTX.

Volatile organic compounds (VOCs), such as benzene, toluene and xylenes (BTX), are recognized as environmental contaminants due to their acute and chronic toxic effects, and toluene is a substance contained in products used in inhalants. In this way, methods able to determine these substances in non-invasive matrices offer great applicability for assessing acute exposure. In this study, a functionalized polymer, chloropropyltrimethoxysilane/polydimethylsiloxane, was evaluated as a potential material to be used in solid-phase microextraction for the quantification of BTX in urine by gas chromatography coupled to mass spectrometry (GC-MS). The method optimization was performed by using fractional factorial planning 2 (4-1) and the Doehlert's experiment. Desorption time and salinity were the most important factors that impact the sensitivity of the method. Spectroscopic and thermogravimetric characterization demonstrated the functionalization of the material and its thermal stability up to 390°C. This allowed it to be used for ~60 analytical cycles without loss of efficiency. The proposed method demonstrated a satisfactory analytical performance to determine the VOCs studied. The protocol agrees with the principles of green analytical chemistry since the procedure reduced the reagents consumed and wastes generated. It represents a promising tool for acute exposure assessment to BTX since urine tests demonstrated its applicability.

Modification of the existing maximum residue levels for flupyradifurone and DFA in okra/lady's finger.

In accordance with Article 6 of Regulation (EC) No 396/2005, FPS Public Health, Food Chain Safety and Environment on behalf of Belgium (evaluating Member State, EMS) submitted an application to modify the existing maximum residue levels (MRLs) for the active substance flupyradifurone and its metabolite difluoroacetic acid (DFA) in okra/lady's finger. The data submitted in support of the request were found sufficient to derive MRL proposals for the crop under consideration. The potential contribution of DFA residues in okra/lady's finger from the soil uptake was also estimated. Adequate analytical methods for enforcement are available to control the relevant residues in the crop under consideration. Based on the risk assessment results, EFSA concluded that the long‐term intake of residues of flupyradifurone and of its soil metabolite DFA resulting from the use of flupyradifurone is unlikely to present a risk to consumer health. Due to the lack of proper consumption data of okra/lady's finger, the acute exposure assessment could not be reliably undertaken but due to this crop being a minor commodity it is unlikely that acute consumer intake concerns will be associated with this crop.

Estimating hourly PM2.5 concentrations in Beijing with satellite aerosol optical depth and a random forest approach

Assessing short-term exposure to PM2.5 requires the concentration distribution at a high spatiotemporal resolution. Abundant researches have derived the daily predictions of fine particles, but estimating hourly PM2.5 is still a challenge restrained by the input data. The recent aerosol optical depth (AOD) product from Himawari-8 provides hourly satellite observations informative to modelling. In this study, we developed separate random forest models with and without AOD and combined the estimates to obtain a full-coverage hourly PM2.5 distribution. 10-fold cross validation R2 ranged from 0.92 to 0.95 and root mean square errors from 14.1 to 16.9 μg/m3, indicating the good model performance. Spatial convolutional layers of PM2.5 measurements and temporal accumulation effects of meteorological features were added into the model. They turned out to be of the most important predictors and improved the performance significantly. Finally, we mapped hourly PM2.5 at a 1-km resolution in Beijing during a pollution episode in 2019 and studied the pollution pattern. The study proposed a method to obtain 24-h full-coverage hourly PM2.5 estimates which are useful for acute exposure assessment in epidemiological researches.