Bayesian hierarchical modeling and inference for mechanistic systems in industrial hygiene.

A series of experiments in stationary and moving passenger rail cars were conducted to measure removal rates of particles in the size ranges of SARS-CoV-2 viral aerosols and the air changes per hour provided by existing and modified air handling systems. Such methods for exposure assessments are customarily based on mechanistic models derived from physical laws of particle movement that are deterministic and do not account for measurement errors inherent in data collection. The resulting analysis compromises on reliably learning about mechanistic factors such as ventilation rates, aerosol generation rates, and filtration efficiencies from field measurements. This manuscript develops a Bayesian state-space modeling framework that synthesizes information from the mechanistic system as well as the field data. We derive a stochastic model from finite difference approximations of differential equations explaining particle concentrations. Our inferential framework trains the mechanistic system using the field measurements from the chamber experiments and delivers reliable estimates of the underlying physical process with fully model-based uncertainty quantification. Our application falls within the realm of the Bayesian "melding" of mechanistic and statistical models and is of significant relevance to environmental hygienists and public health researchers working on assessing the performance of aerosol removal rates for rail car fleets.

Opportunities and Challenges Associated with the Uptake of Residential Clean Fuel Usage.

PURPOSE OF REVIEW: Almost 3 billion people worldwide use solid fuel for cooking and heating. This review examines (i) household energy practices and infrastructures and their influence on fuel usage in different contexts; (ii) barriers in adoption of household clean energy technologies and uses in diverse settings and population groups and (iii) potential air pollution exposure reduction in homes through using processed fuel. RECENT FINDINGS: Population health burden from solid fuel combustion-derived particulate air pollution has been estimated in several low- and middle-income countries. However, such studies have not been carried out in high income countries (e.g., UK). Irrespective of the region, fuel prices are the most dominant factor influencing the choice of fuel. Laboratory studies suggest processed fuel - pellets and briquettes - reduce particulate matter emissions by 70-80% and can be a promising alternative. Adoption of clean fuels for domestic energy needs facilitates progress towards five of the UN Sustainable Development Goals (SDGs). There is evidence that a variety of factors, including cost savings, encourage and hinder such uptake. These factors include price fluctuations, expenses, and the usage of clean fuels. Due to their distinct development scenarios, more expansive policy frameworks, and political economies of energy, these determinants are localized in character and differ significantly amongst economies. Therefore, in order to create innovative plans for the adoption of clean fuel use, strategies centred on local settings must be developed while keeping broad socio-technical and socio-economic issues in mind. Solid fuel processing - pelletization and briquetting - have the potential to reach Liquefied Petroleum Gas (LPG)-like emissions, and could be a potential strategy to mitigate exposure to household air pollution.

Blood-lead level in humans and drug addiction: a comprehensive study in Iran.

Drug abuse has a high prevalence worldwide and causes many health-related disorders. There are limited human exposure studies on establishing lead exposure levels and their propensity for drug addiction. In the present study, blood samples were tested for lead (Pb) concentrations in illicit drug users together with the related symptoms in comparison with control group of non-drug users. The study was performed on 250 volunteers divided equally in four drug groups, namely, opioids, hashish, methadone, and methamphetamine, and one control group of non-drug users. Participants were recruited from drug addiction clinics and camps in Kashan city, Iran, who were using drugs continuously for more than 1 year. Control group was recruited from companions of the patients with no drug use history. In the investigated groups of drug users, the highest blood-lead level (BLL) concentrations were observed in the opioid group (mean 37.57 µg/dL) with almost 3.7 times higher than in the control group (mean 3.39 µg/dL). In the methamphetamine group, type of occupation had the significant association with BLL concentrations. The positive correlation was revealed in the opioid and methadone groups for BLL concentrations and the duration of drug usage. In the opioid group, the highest BLL concentrations were observed among users who used both methods of drug use: smoking and eating. Also, several behavioral and life-style factors were identified which influence the blood-lead concentration in the drug users. The results of our study revealed that the BLL concentrations in investigated drug users' groups were significantly higher than in the control group (P < 0.001). That can be related with the Pb contents in illicitly used drugs. Apart other adverse health effects, long-term illicit drug use might cause to lead poisoning.

Subchronic exposure to ambient PM 2.5 impairs novelty recognition and spatial memory.

Air pollution remains a great challenge for public health, with the detrimental effects of air pollution on cardiovascular, rhinosinusitis, and pulmonary health increasingly well understood. Recent epidemiological associations point to the adverse effects of air pollution on cognitive decline and neurodegenerative diseases. Mouse models of subchronic exposure to PM 2.5 (ambient air particulate matter < 2.5 µm) provide an opportunity to demonstrate the causality of target diseases. Here, we subchronically exposed mice to concentrated ambient PM 2.5 for 7 weeks (5 days/week; 8h/day) and assessed its effect on behavior using standard tests measuring cognition or anxiety-like behaviors. Average daily PM 2.5 concentration was 200 µg/m 3 in the PM 2.5 group and 10 µg/m 3 in the filtered air group. The novel object recognition (NOR) test was used to assess the effect of PM 2.5 exposure on recognition memory. The increase in exploration time for a novel object versus a familiarized object was lower for PM 2.5 -exposed mice (42% increase) compared to the filtered air (FA) control group (110% increase). In addition, the calculated discrimination index for novel object recognition was significantly higher in FA mice (67 %) compared to PM 2.5 exposed mice (57.3%). The object location test (OLT) was used to examine the effect of PM 2.5 exposure on spatial memory. In contrast to the FA-exposed control mice, the PM 2.5 exposed mice exhibited no significant increase in their exploration time between novel location versus familiarized location indicating their deficit in spatial memory. Furthermore, the discrimination index for novel location was significantly higher in FA mice (62.6%) compared to PM 2.5 exposed mice (51%). Overall, our results demonstrate that subchronic exposure to higher levels of PM 2.5 in mice causes impairment of novelty recognition and spatial memory.

Asthma symptoms, spirometry and air pollution exposure in schoolchildren in an informal settlement and an affluent area of Nairobi, Kenya.

BACKGROUND: Although 1 billion people live in informal (slum) settlements, the consequences for respiratory health of living in these settlements remain largely unknown. This study investigated whether children living in an informal settlement in Nairobi, Kenya are at increased risk of asthma symptoms. METHODS: Children attending schools in Mukuru (an informal settlement in Nairobi) and a more affluent area (Buruburu) were compared. Questionnaires quantified respiratory symptoms and environmental exposures; spirometry was performed; personal exposure to particulate matter (PM2.5) was estimated. RESULTS: 2373 children participated, 1277 in Mukuru (median age, IQR 11, 9-13 years, 53% girls), and 1096 in Buruburu (10, 8-12 years, 52% girls). Mukuru schoolchildren were from less affluent homes, had greater exposure to pollution sources and PM2.5. When compared with Buruburu schoolchildren, Mukuru schoolchildren had a greater prevalence of symptoms, 'current wheeze' (9.5% vs 6.4%, p=0.007) and 'trouble breathing' (16.3% vs 12.6%, p=0.01), and these symptoms were more severe and problematic. Diagnosed asthma was more common in Buruburu (2.8% vs 1.2%, p=0.004). Spirometry did not differ between Mukuru and Buruburu. Regardless of community, significant adverse associations were observed with self-reported exposure to 'vapours, dusts, gases, fumes', mosquito coil burning, adult smoker(s) in the home, refuse burning near homes and residential proximity to roads. CONCLUSION: Children living in informal settlements are more likely to develop wheezing symptoms consistent with asthma that are more severe but less likely to be diagnosed as asthma. Self-reported but not objectively measured air pollution exposure was associated with increased risk of asthma symptoms.

Experimental studies of particle removal and probability of COVID-19 infection in passenger railcars.

A series of experiments in stationary and moving passenger railcars was conducted to measure the removal rates of particles in the size ranges of SARS-CoV-2 viral aerosols, and the air changes per hour provided by the existing and modified air handling systems. The effect of ventilation and air filtration systems on removal rates and their effects on estimated probability (i.e., risk) of infection was evaluated in a range of representative conditions: (1) for two different ratios of recirculated air (RA) to outdoor air (OA) (90:10 RA:OA and 67:33 RA:OA); (2) using minimum efficiency reporting value (MERV) filters with standard (MERV-8) and increased (MERV-13) filtration ratings; and (3) in the presence and absence of a portable high-efficiency particulate-air (HEPA) room air purifier system operated at clean air delivery rate (CADR) of 150 and 550 cfm. The higher-efficiency MERV-13 filters significantly increased particle removal rates on average by 3.8 to 8.4 hr-1 across particle sizes ranging from 0.3 to 10 µm (p < 0.01) compared to MERV-8 filters. The different RA:OA ratios and the use of a portable HEPA air purifier system had little effect on particle removal rates. MERV-13 filters reduced the estimated probability of infection by 42% compared to the MERV-8 filter. The use of a HEPA-air purifier with a MERV-13 filter causes a 50% reduction in the estimated probability of infection. Upgrading the efficiency of HVAC filters from MERV-8 to MERV-13 in public transit vehicles is the most effective exposure control method resulting in a clear reduction in the removal rates of aerosol particles and the estimated probability of infection.

Assessing variability of aerosols generated from e-Cigarettes.

While some in vitro and in vivo experiments have studied the toxic effects of e-cigarette (e-cig) components, the typical aerosol properties released from e-cigarettes have not been well characterized. In the present study, we characterized the variability in mass concentration and particle size distribution associated with the aerosol generation of different devices and e-liquid compositions in an experimental setup. The findings of this study indicate a large inter-day variability in the experiments, likely due to poor quality control in some e-cig devices, pointing to the need for a better understanding of all the factors affecting exposures in in vitro and in vivo experiments, and the development of standardized protocols for generation and measurement of e-cig aerosols.

Risk analysis of different transport vehicles in India during COVID-19 pandemic.

Due to the airborne nature of viral particles, adequate ventilation has been identified as one suitable mitigation strategy for reducing their transmission. While 'dilution of air by opening the window' has been prescribed by national and international health agencies, unintended detrimental consequences might result in many developing countries with high ambient air pollution. In the present study, PM2.5 exposure concentration and probability of mortality due to PM2.5 in different scenarios were assessed. A COVID airborne infection risk estimator was used to estimate the probability of infection by aerosol transmission in various commuter micro-environments: (a) air conditioned (AC) taxi (b) non-AC taxi (c) bus and (d) autorickshaw. The following were the estimated exposure concentrations in the four types of vehicles during pre-lockdown, during lockdown, and lost-lockdown: AC taxi cars (17.16 µg/m3, 4.52 µg/m3, and 25.09 µg/m3); non-AC taxis: (28.74 µg/m3, 7.56 µg/m3, 42.01 µg/m3); buses (21.79 µg/m3, 5.73 µg/m3, 31.86 µg/m3) autorickshaws (51.30 µg/m3, 3.50 µg/m3, 75 µg/m3). Post-lockdown, the probability of mortality due to PM2.5 was highest for autorickshaws (5.67 × 10-3), followed by non-AC taxis (2.07 × 10-3), buses (1.39 × 10-3), and AC taxis (1.02 × 10-3). This order of risk is inverted for the probability of infection by SARS-COV-2, with the highest for AC taxis (6.10 × 10-2), followed by non-AC taxis (1.71 × 10-2), buses (1.42 × 10-2), and the lowest risk in autorickshaws (1.99 × 10-4). The findings of the present study suggest that vehicles with higher ventilation or air changes per hour (ACH) should be preferred over other modes of transport during COVID-19 pandemic.

Impact assessment of clean cookstove intervention in Gujarat, India: a potential case for corporate social responsibility (CSR) funding.

Exposure to indoor air pollutants released from traditional cookstoves in rural Indian households is a matter of great concern. While there are various studies over several decades focused towards intervention strategies for reducing air pollutants, limited literature exists towards the identification of appropriate methodology for feasible intervention, adoption and usage of improved cookstoves (ICS). In the present study, PM2.5 and CO microenvironment concentrations are estimated in households using traditional and improved cookstove (NEERDHUR). The reduction in PM2.5 and CO microenvironment concentrations after the introduction of ICS was found to be 89-94% and 35-57%, respectively. Information-education-communication (IEC) activity was used as a tool to increase the adoption and usage rate in the ICS using households. The cost-benefit analysis was also performed to check the benefits of ICS use, and the benefit-cost ratio was found to be 3 to 4 times. Findings of the study suggest that, although the ICS intervention could significantly improve the indoor air quality, however, it fails to comply with the permissible safe limits; further focus on greener fuels and ventilation characteristics is suggested. The outcomes from the study can help decision-makers, corporate social responsibility fund mobilizers and policymakers for effective policy advocacy to design efforts by promoting clean cooking interventions and linking and mapping these with national missions and flagship programs.

Influence of the Inclusion of Ignition Stage Emissions in the Development of Emission Factors for Coal Cookstoves Used in India.

Coal is used widely for domestic cooking in many regions of India, which contributes significantly to the particulate matter (PM < 2.5 µm) and CO levels in ambient and indoor air. Modeling and inventorization require the use of emission factors (EFs) for cookstoves, which are specific to fuel type and cookstove design. These are usually not available or are available for emissions under steady state combustion conditions following some protocols that are end-use-specific. In this study, two types of cookstoves are deployed, and PM < 2.5 µm and CO emissions are measured for a combustion cycle that includes an initial ignition stage, a flaming stage, and a smoldering stage. EFs are estimated for PM < 2.5 µm and CO for each of these stages of the combustion cycle and indicate a 5-9-fold increase for PM < 2.5 µm when emissions from the ignition stage are included. Elemental carbon and organic carbon analyses are presented for PM < 2.5 µm using two protocols, namely, IMPROVE_A and DIN-19539. The EFs developed for the complete combustion cycle may be used to better represent the impact of coal cookstoves on the ambient air quality and for a more realistic assessment of health effects for exposure in kitchens.