Quantitative Health Risk Assessment Research Articles

Health Risk Assessment from Exposure to Ambient Volatile Organic Compounds (VOCs) at a Truck Tire Factory in the Yangtze River Delta, China

Occupational health risk assessments of exposure to VOCs still need to be extensively studied to improve the safety standards in the industry. Based on the monitoring of organic pollutants at various workstations in a truck tire factory in Jiangsu Province, both semi-quantitative and quantitative health risk assessment methods were employed to assess health risk levels. The findings indicated that VOCs were categorized into five classes, which included alkanes, aromatics, halocarbons, carbon disulfide, and oxygenated volatile organic compounds (OVOCs). The highest concentration of total volatile organic compounds (TVOCs) was found in shaping workshop; alkanes were the most abundant class (74.2%), followed by aromatics (24.02%) and OVOCs (1.96%). Although the results of the semi-quantitative risk assessment showed that most of the organic compounds had low R values, various kinds of VOCs were detected; particularly, many harmful organic compounds (such as toluene, ethyl benzene) were detected in all the sampling sites. The quantitative risk in the calendering and vulcanizing workshop exceeded the acceptable level; both the carcinogenic risk of ethylbenzene in the tire-strip storage room, and trichloroethylene and perchloroethylene in the calendering workshop were unacceptable. Thus, the calendering and vulcanizing processes in rubber tire manufacturing should be priority-controlled processes.

Inhalation bioaccessibility of imidacloprid in particulate matter: Implications for risk assessment during spraying

Adverse health outcomes due to the inhalation of pesticide residues in atmospheric particulate matter (PM) are gaining global attention. Quantitative health risk assessments of pesticide inhalation exposure highlight the need to understand the bioaccessibility of pesticide residues. Herein, the inhalation bioaccessibility of imidacloprid in PM was determined using three commonly used in vitro lung modeling methods (Artificial Lysosomal Fluid, Gamble Solution, and Simulated Lung Fluid). To validate its feasibility and effectiveness, we evaluated the bioavailability of imidacloprid using a mouse nasal instillation assay. The in vitro inhalation bioaccessibility of imidacloprid was extracted using Gamble Solution with a solid–liquid ratio of 1/1000, an oscillation rate of 150 r/min, and an extraction time of 24 h, showed a strong linear correlation with its in vivo liver-based bioavailability (R2 =0.8928). Moreover, the margin of exposure was incorporated into the inhalation exposure risk assessment, considering both formulations and nozzles. The inhalation unit exposure of imidacloprid for residents was 0.95–4.09 ng/m3. The margin of exposure for imidacloprid was determined to be acceptable when considering inhalation bioaccessibility. Taken together, these results indicate that the inhalation bioaccessibility of pesticides should be incorporated into assessments of human health risks posed by PM particles.

Pesticide contamination pattern from Morocco, insights into the surveillance situation and health risk assessment: a review.

The widespread application of pesticides in Morocco's agriculture renders their monitoring in food and environmental samples very necessary. Recent years have witnessed a growing interest in reporting studies related to the monitoring of pesticide residues in food, water, groundwater, and soil as well as their quantitative health risk assessment. Most published studies have been done by university researchers. However, the lack of research reproducibility remains a problem that considerably limits the possibility of exploiting data from the literature. Our study involves an extensive literature review utilizing search engines with keywords like "pesticide residues," "monitoring," "vegetables and fruits," "water and soil," "risk assessment," and "Morocco" from 2009 to 2023. Analysis of pesticide residues in foodstuffs and environmental samples highlights concerns over compliance with EU regulations, the health risks associated with pesticide exposure, and the necessity for comprehensive monitoring and risk assessment strategies. This paper could help influence policies to develop a strategy and action plan for the sound management of pesticides, including measures to reduce their use, raise awareness, and monitor compliance. Also, this paper could be useful for scientists interested in understanding the current situation and challenges regarding pesticide residues in Morocco, as well as countries with which commercial links exist.

Quantitative health risk assessment of microbial hazards from water sources for community and self-supply drinking water systems

In low and medium income countries (LMIC) drinking water sources (wells and boreholes) often contain a high number of pathogenic microorganisms, that can pose significant human and environmental health risks. In this study, a quantitative microbial risk assessment approach based on existing literature was conducted to evaluate and compare the quantitative health risks associated with different age groups using various drinking water supply systems. Results showed that both community-supply and self-supply modes exhibit similar levels of risk. However, the self-supply water source consistently showed higher risks compared to the community-supply one. Borehole water was found to be a more suitable option than well water, consistently showing between 5 and 8 lower health risks for E. coli and fecal coliform levels, respectively. The sensitivity analysis further showed the importance of prioritizing the reduction of E. coli concentration in well water and fecal coliform concentration in borehole water. This study offers a fresh perception on quantifying the impact of exposure concentration and age groups, shedding light on how they affect environmental health risks. These findings provide valuable insights for stakeholders involved in the management and protection of water sources.

Human health risk-based soil generic assessment criteria of representative perfluoroalkyl acids (PFAAs) under the agricultural land use in typical Chinese regions

Perfluoroalkyl acid substances (PFAAs), such as perfluorobutanoic acid (PFBA), perfluorobutanoic sulfonic acid (PFBS), perfluorooctane acid (PFOA) and perfluoroooctane sulfonic acid (PFOS) are frequently detected in the global environment and can cause potential health hazards even at low levels. In this study, quantitative human health risk assessment was undertaken to derive soil generic assessment criteria (GAC) for four PFAAs under the agricultural land scenario in the evaluated Chinese regions, which considered multiple exposure pathways including vegetables consumption, dermal absorption, ingestion of soil and dust, and exposure from non-soil sources. It is showed that the calculated GAC for four PFAAs in Guangdong and Shandong Provinces were less stringent than those in Zhejiang and Jiangsu Provinces, and Shanghai City, owing to the low exposure from non-soil sources in former two provinces. In addition, GAC of PFOS were the most stringent in the range of 0.28–0.50 μg kg−1 in the studied regions, followed by PFOA (1.36–2.20 μg kg−1), PFBA (42.59–68.03 μg kg−1) and PFBS (474.59–749.60 μg kg−1), mainly attributable to significantly more stringent toxicological values of PFOA and PFOS. Correspondingly, the potential health hazards exist for PFOA in the studied regions except Guangdong Province, and PFOS only in Zhejiang and Jiangsu Provinces as indicated by the hazard quotients ranging from 1.04 to 19.49, but no health hazards are identified for PFBA and PFBS. The dominant exposure pathway was found to be consumption of vegetables and attached soil for PFBA and PFBS, contributing to more than 93% of the total exposure, compared to 49.91–76.69% for PFOA and PFOS due to significant exposure from non-soil sources levels. Overall, this study provides a technical reference on how to derive scientifically justifiable soil GAC for representative PFAAs for maintaining and assessing soil quality and food safety internationally under the agricultural land use.

What is an exposure-response curve?

Exposure-response curves are among the most widely used tools of quantitative health risk assessment. However, we propose that exactly what they mean is usually left ambiguous, making it impossible to answer such fundamental questions as whether and by how much reducing exposure by a stated amount would change average population risks and distributions of individual risks. Recent concepts and computational methods from causal artificial intelligence (CAI) and machine learning (ML) can be applied to clarify what an exposure-response curve means; what other variables are held fixed (and at what levels) in estimating it; and how much inter-individual variability there is around population average exposure-response curves. These advances in conceptual clarity and practical computational methods not only enable epidemiologists and risk analysis practitioners to better quantify population and individual exposure-response curves but also challenge them to specify exactly what exposure-response relationships they seek to quantify and communicate to risk managers and how to use the resulting information to improve risk management decisions.

Quantitative analysis and health risk assessment of bisphenols in selected canned foods using the modified QuEChERS method coupled with gas chromatography-mass spectrometry

A QuEChERS-based extraction method, followed by derivatization prior to gas chromatography-mass spectrometric detection, was used to determine the presence and levels of bisphenol A and four of its derivatives in canned fish, baked beans and corned beef. The best conditions for derivatization of the five bisphenols were found to be 25°C over 60 min using a multivariate procedure based on central composite design and bis(trimethylsilyl) trifluoroacetamide as the derivatizing agent. Good method validation parameters were observed with recoveries ranging from 80% to 98% at three spiking levels, while method detection and quantitation limits were in the 0.794–3.81 and 2.41–11.5 µg kg−1 range, respectively. Bisphenol A was detected in all food categories (16.5–191 µg kg−1) while bisphenol B was detected in baked beans only with concentration ranges of 15.4–49.2 µg kg−1. The estimated daily intake for bisphenol A due to consumption of all the three food categories was estimated at 0.57 µg kg−1 bw per day. This value was within the temporary tolerable daily intake set by the European Union. A health risk assessment prediction using the hazard quotient showed that the potential for non-carcinogenic effects in adults due to a lifetime consumption of the studied canned foods was minimal but detrimental to vulnerable groups especially babies. In this regard, detection of these bisphenols in the studied food samples remains a concern and regular monitoring is necessary to ensure they remain within permissible migration levels.

Strengthening Urban Informal Trading and Improving the Health of Vendors: An Integrated Management Model

Within the urban areas, especially the central business districts, informal trading is growing in large numbers, and the informal vendor's health is also at risk. Despite various frameworks developed for this industry, there are few guidance and implementation strategies on how to accomplish better-managed informal trading, mostly one that entails better occupational settings. The goal of the proposed model is to improve the working conditions for informal vendors in South Africa by redesigning the current informal trading management approach, thus ensuring a healthy workplace. An evidence-based approach was used to inform the development of this model. This paper outlines the current challenges of informal vendors in urban areas as per the quantitative health risk assessment study that was conducted in 16 markets amongst 617 informal food vendors in the inner city of Johannesburg, South Africa. The study investigated the respiratory health caused by air pollution and associated risk factors. Findings revealed a lack of infrastructure and higher exposure to air pollution, resulting in respiratory ill-health amongst outdoor vendors as compared to indoor vendors. The vendors were more exposed to particulate matter pollution in the spring and winter seasons as compared to the autumn and summer seasons. Furthermore, the upper respiratory symptoms were statistically significant to the type of work location (indoor/outdoor), type of cooking fuel, duration of work, frequency of hand hygiene, and wearing of protective equipment. An informal vendors' integrated management model that encompasses a specific informal food vendor's directorate was developed with five main components: the reviewing of informal vendors' legislation, the restructuring of designated vending or trading sites, space allocation and occupancy, vendors' training and skills development, and the sustainability of vending sites and vendors' health. The status revealed the legislation fragmentation of the informal vendors' activities. The goal of this informal vendors' "healthy workplace management model" is to inform government responses to the current challenges of the informal vendors' sector, as well as to guide policies and actions to reduce ill-health in the industry and to avoid disruptions to informal food supply chains, which are critical in the food sector. This model is explained well and documented for easier implementation in local governments. This paper contributes to the extant literature on street vendors and future management strategies of this trade.

Trace element geochemical imprints and multi-path health risk assessment of potentially toxic elements in soils from the polymetallic area of tashan-jatau, northwestern nigeria

The occurrence of Potentially toxic elements (PTEs) in the soil phase may portend environmental, ecological and health-related risks. Hence, this study has combined high-precision geochemical analyses (X-ray fluorescence (XRF) and inductively Coupled Plasma Mass Spectrometry (ICP-MS)), quantitative soil pollution indices and health risk assessment modelling for a holistic and precise assessment of the intrinsic vulnerability of the soil system to contamination. Geochemical analysis showed that the soils are highly enriched with PTEs such as V (mean = 449.5 mg/L), Cr (mean = 529.9 mg/L), Cu (mean = 374.4 mg/L), Sr (mean = 1365.3 mg/L), Zr (mean = 2703 mg/L), Zn (mean = 282.5 mg/L), and Pb (mean = 127.3 mg/L). Quantitative soil pollution assessment (contamination factor and enrichment factor) revealed that besides mining, the distribution and association between trace elements and oxides were from surface environmental conditions (including mobility potential, leaching metal-complexation, weathering and oxidation of parent material). Health risk assessment based on hazard quotient and hazard index revealed that the inhabitants are generally more exposed to risks from toxic elements ingestion than dermal contact and inhalation; the children are vulnerable to risks than adults. The cancer risks from ingestion and dermal contact of As and Cr for both children and adults are relatively higher (> 1.0E−04) than the acceptable range; although the children population seems to be more susceptible to cancer risks due to lower body weight.

Assessing the utilization potential of pumped-out minewater for potability in the water-stressed coal mining region of Jharia, India: a quantitative, qualitative and probabilistic health risk assessment

Assessing the utilization potential of pumped-out minewater for potability in the water-stressed coal mining region of Jharia, India: a quantitative, qualitative and probabilistic health risk assessment

Quantitative risk assessment for bacterial community in residential kitchens

Health risks posed by bacteria in residential kitchens have been underappreciated in public opinions despite the fact that residential kitchens are a significant hotspot of foodborne diseases. Previous studies on quantitative health risk assessment for real residential kitchens are limited. To this end, the present study first characterized the bacterial communities in 13 residential kitchens in different cities across China with the nanopore sequencing technology. We found that while the overall relative abundance of the 18 detected pathogens was low (5.6%), the potential health risks posed by the pathogens were not neglectable. The pathogens were associated with 17 diseases that affect more than 7 body systems. We selected 3 representative pathogens, i.e., Staphylococcus aureus, Escherichia coli, and Salmonella enterica and quantified the health risks via the quantitative microbial risk assessment (QMRA) framework. It is shown the health risks on most detected surfaces were above the acceptable safety target (10−6) with those on handles being the highest. While common disinfectant-containing household detergents are seemingly capable of reducing health risks to an acceptable level, developing green and labor-saving disinfecting techniques is needed.

Assessment of the risk of Legionella pneumophila in water distribution systems in hospitals of Tehran city.

When a sensitive host inhales aerosols containing these bacteria, Legionella infection occurs. Therefore, monitoring and assessing Legionella in the environment and water distribution systems of such places are critical due to the prone population in hospitals. However, the health risks of Legionella bacteria in the environment are not adequately evaluated. In this study, for hospitalized patients, we performed a quantitative health risk assessment of Legionella in selected hospitals in Tehran city using two scenarios of shower and toilet faucet exposure. This study identified Legionella in 38 cases (38%) out of 100 samples collected from toilet faucets and showers in 8 hospitals. The information gathered was used for quantitative microbial risk assessment (QMRA). The microbial load transmitted by inhalation was calculated using the concentration of Legionella in water. Other exposure parameters (inhalation rate and exposure time) were obtained using information from other studies and the median length of hospital stay (3.6days). The exponential model was used to estimate the risk of infection (γ = 0.06) due to Legionella pneumophila (L. pneumophila) inhalation for each exposure event. For the mean concentration obtained for Legionella (103CFU/L), the risk of infection for toilet faucets and showers was in the range of 0.23-2.3 and 3.5-21.9, respectively, per 10,000 hospitalized patients. The results were compared with the tolerable risk level of infection determined by the US EPA and WHO. The risk values exceeded the WHO values for waterborne pathogens in hospitals in both exposure scenarios. As a result, our QMRA results based on monitoring data showed that despite using treated water (from distribution networks in the urban areas) by hospitals, 38% of the samples were contaminated with Legionella, and faucets and showers can be sources of Legionella transmission. Hence, to protect the health of hospitalized patients, the risk of Legionella infection should be considered.

Polycyclic Aromatic Hydrocarbon in Fruits and Vegetables Grown in Turkey: Quantitative Analysis, Dietary Exposure, and Health Risk Assessment

The quantitative analysis, dietary exposure, and health risks of four European Union (4EU) priority polycyclic aromatic hydrocarbons (PAH4) were investigated in different varieties of vegetables in Turkey. PAH congeners were analyzed by an in house validated HPLC method. Low amounts of PAHs were detected in all examined vegetables. The leafy vegetables showed higher contamination among all types of vegetables. The sum of PAH4 (benzo[a]pyrene, benzo[a]anthracene, chrysene, and benzo[b]fluoranthene) levels of leafy vegetables such as broccoli and cauliflower were determined as 0.77 and 0.59 μg/kg, respectively. The peels were found to be more contaminated than the cores in root and fruit vegetables. Among the root vegetables, maximum PAH4 concentration was found 0.73 μg/kg in potato peel. The highest level of individual PAH in all vegetables examined was Benz[a]anthracene (BaA), and its value was 0.38 ± 0.16 μg/kg in cauliflower. Benzo[a]pyrene (BaP), the most representative of the carcinogenic PAHs, was most commonly detected in all samples. Benzo(b)fluoranthene (BbF) and chrysene (CHR) showed relatively lower levels in all studied samples. Human dietary exposure to PAH by consumption of the fruits and vegetables was determined considering the estimated daily intake. The study revealed that the estimated incremental lifetime cancer risk indicates a low health risk for children and adult consumers. The present paper is the first attempt concerning quantitative analysis and health risk assessment of polycyclic aromatic hydrocarbons in fruits and vegetables grown in Turkey.

Impacts of risk assessment data, assumptions, and methods: Considering the evidence for diacetyl and 2,3-pentanedione.

The articles published as part of the Frontiers in Public Health research topic, “Investigating exposures and respiratory health in coffee workers” present research findings that better characterize exposures to diacetyl and 2,3-pentanedione and inform our understanding of the health risks posed by these exposures. Although various research groups and organizations have conducted risk assessments to derive occupational exposure limits (OELs) for diacetyl, differences in the data used and assumptions made in these efforts have resulted in a wide range of recommended OELs designed to protect human health. The primary drivers of these differences include the decision to use data from human or animal studies in conducting a quantitative risk assessment, and the application of uncertainty factors (UF) to derive an OEL. This Perspectives paper will discuss the practical implications of these decisions, and present additional commentary on the potential role that the recent investigation of human exposures to relatively low concentrations of α-diketones, specifically diacetyl and 2,3-pentanedione, may play in supporting qualitative or quantitative human health risk assessments.

Health Risk-Oriented Source Apportionment of Hazardous Volatile Organic Compounds in Eight Canadian Cities and Implications for Prioritizing Mitigation Strategies.

Traditionally, environmental authorities make regulatory policies for controlling volatile organic compound (VOC) pollution based on the mitigation of dominant VOC sources. However, the emission from each VOC source has a unique combination of VOC species of different toxicities. Without quantitatively assessing the health risk associated with each source, the effectiveness of the mitigation policy could be undermined. To address this shortcoming, we developed a new health risk-oriented source apportionment method that can provide quantitative health risk assessment and source-specific mitigation strategies for hazardous VOCs. We estimated that the integrated inhalation cancer risk (ICR) of hazardous VOCs was 7.7 × 10-5 in Western Canada, indicating a 100% likelihood of exceeding Health Canada's acceptable risk level (1.0 × 10-5). Anthropogenic sources were responsible for 56.3-73.8% of cancer risks across eight Canadian cities except for the regional background island, where natural sources contributed over 77% to the integrated ICR. Thus, substantial environmental and health cobenefits could be achieved via reducing the ambient levels of benzene and 1,3-butadiene by 39.3-75.7 and 14-69.3%, respectively, and mitigating emissions from fuel combustion (by 31.3-54.1%), traffic source (3.0-36.8%), and other anthropogenic sources (5.3-20.1%) in Western Canada. Our study has significant implications for prioritizing air pollution mitigation policies, especially for quantitative reduction of hazardous air pollutants.

Dermal Exposure to Hazardous Chemicals in Baby Diapers: A Re-Evaluation of the Quantitative Health Risk Assessment Conducted by The French Agency for Food, Environmental and Occupational Health and Safety (ANSES).

In January 2019, the French Agency for Food, Environmental and Occupational Health and Safety (ANSES) published an opinion on risks related to the presence of hazardous chemicals in infant diapers. ANSES found that health reference values were largely exceeded for polycyclic aromatic hydrocarbons (PAHs), dioxins (PCCD/Fs) and dioxin-like polychlorobiphenyls (DL-PCBs). The levels of formaldehyde and some fragrances were also considered potentially unsafe. Therefore, ANSES concluded that actions have to be taken to restrict levels of these contaminants in diapers. Under the exposure scenario deemed the most reliable by ANSES, estimates of cancer risks of the most potent PAHs detected in diapers exceeded 10−3 and hazard quotients for neurobehavioral effects attained values up to 66. Regarding dioxins and DL-PCBs, ANSES derived a hazard quotient of 12 for the risk of decreased sperm count at adult age. The aim of this study was to examine whether the exposure and risk assessment conducted by ANSES contained potential flaws that could explain such a high exceedance of health reference values. This study also put into perspective the exposure from diapers with that from breast milk whose benefits for children’s health are undisputable despite contamination by PAHs, dioxins and DL-PCBS.

Quantitative Health Risk Assessment of the Chronic Inhalation of Chemical Compounds in Healthcare and Elderly Care Facilities.

Previous studies have described the chemical pollution in indoor air of healthcare and care facilities. From these studies, the main objective of this work was to conduct a quantitative health risk assessment of the chronic inhalation of chemical compounds by workers in healthcare and elderly care facilities (hospitals, dental and general practitioner offices, pharmacies and nursing homes). The molecules of interest were 36 volatile and 13 semi-volatile organic compounds. Several professional exposure scenarios were developed in these facilities. The likelihood and severity of side effects that could occur were assessed by calculating the hazard quotient for deterministic effects, and the excess lifetime cancer risk for stochastic effects. No hazard quotient was greater than 1. Three compounds had a hazard quotient above 0.1: 2-ethyl-1-hexanol in dental and general practitioner offices, ethylbenzene and acetone in dental offices. Only formaldehyde presented an excess lifetime cancer risk greater than 1 × 10−5 in dental and general practitioner offices (maximum value of 3.8 × 10−5 for general practitioners). The health risk for chronic inhalation of most compounds investigated did not appear to be of concern. Some values tend to approach the acceptability thresholds justifying a reflection on the implementation of corrective actions such as the installation of ventilation systems.

Chlordecone: development of a physiologically based pharmacokinetic tool to support human health risks assessments

Chlordecone (CD; Kepone™) is a carcinogenic organochlorine insecticide with neurological, reproductive, and developmental toxicity that was widely used in the French West Indies (FWI) from 1973 to 1993 to fight banana weevils. Although CD has not been used there for more than 25 years, it still persists in the environment and has polluted the waterways and soil of current and older banana fields. Today, human exposure to CD in the FWI mainly arises from consuming contaminated foodstuffs. The aims of this study were to develop a physiologically based pharmacokinetic (PBPK) model in the rat and extrapolate it to humans based on available pharmacokinetic data in the literature. A comparison of simulations using the rat model with published experimental datasets showed reasonable predictability for single and repetitive doses, and, thus, it was extrapolated to humans. The human PBPK model, which has seven compartments, is able to simulate the blood concentrations of CD in human populations and estimate the corresponding external dose using the reverse dosimetry approach. The human PBPK model will make it possible to improve quantitative health risk assessments for CD contamination and reassess the current chronic toxicological reference values to protect the FWI population.

Methodological approaches for quantitative assessment of health risk associated with the labour process strength

Introduction. Labour employment of the population is increasingly associated with mental activity and is characterized by increasing stress. The article presented and tested methodical approaches to the quantitative health risk assessment associated with the labour process strength (LPS), taking into account it’s detailing by type of load. Materials and methods. In the course of the work, analytical, epidemiological, and statistical methods were used. The proposed approaches were tested on the example of assessing the health risk of male employees of oil and gas production operators (OGPO), aged from 26 to 59 years (average age: 44.51 ± 8.01 years) with work experience in the profession of from 3 up to 33 years old (average experience 17.05 ± 8.89 years). Results. The developed algorithm for assessing the health risk associated with LPS includes using a tool (checklist), which will allow, along with a comprehensive assessment, assessing detailed types of loads - intellectual, emotional, sensory, monotony mode of work. The checklist contains the specified characteristics of the LPS assessment indicators and criteria that allow us to weigh the degree of tension (0 - there is no effect on this indicator, 4 - the influence on the indicator is most pronounced). The procedure provides for a quantitative assessment of occupational health risk and determination of the contribution of detailed load types to the formation of risk. The results of testing confirm the validity of the proposed approaches. The risk of developing a gastric ulcer and duodenal ulcer due to sensory load was revealed to be 2 • 10-2 and was classified as medium. As a result of exposure to sensory load and operating mode, the risk of developing atherosclerosis is 5.7 • 10-2 and 9.8 • 10-2, respectively, and classified as high. The risk of developing atherosclerosis associated with exposure to two significant LPS components is 14.9 ∙ 10-2. In this case, the contribution of the load associated with the mode of work in the development of atherosclerosis is more significant (66%) than the sensory (34%) load. Conclusion. The developed methods to assess the intensity of the labor process allow moving on to a quantitative assessment of risk and identifying the role (contribution) of individual, detailed types of loads in the formation of occupational health risks, and determining targeted preventive measures.

Emission characteristics and quantitative health risk assessment of bioaerosols in an indoor toilet after flushing under various ventilation scenarios

In the indoor environment, toilet is one of the primary sources of bioaerosol because flushing events can disturb stool materials. Bioaerosol exposure has a significant impact on human health. Therefore, this research focused on systematical investigation of Staphylococcus aureus bioaerosol emission characteristics in an indoor toilet after flushing with time. Then, annual probability of infection and disease burden with time under various ventilation scenarios were determined using a Monte Carlo simulation-based quantitative microbial risk assessment. The results showed that at the initial phase, the highest and lowest bioaerosol concentrations were found in poor and combined ventilation scenarios, respectively. The bioaerosol concentration in natural ventilation scenario was 1.1 times higher than that in mechanical ventilation scenario. However, a decreasing trend was observed after flushing. The adult male's health risks were consistently higher than those of all other exposed persons. However, the maximum and minimum health risks were observed in the poor and combined ventilation scenario, respectively. The health risks in the mechanical ventilation scenario were lower than those in the natural ventilation scenario. However, the health infection risk varied with time: it was unbearable to the U.S. Environmental Protection Agency benchmark at 0 min–15 min after flushing, but it was tolerable after flushing 35 min. Moreover, the disease health burdens were below the World Health Organization benchmark after flushing 20 min to 35 min. This research delivered novel data and provide a guideline for controlling the essential health threats from bioaerosol emissions in various toilet usage scenarios.