Air quality and mental health: evidence, challenges and future directions.

BACKGROUND: Poor air quality is associated with poor health. Little attention is given to the complex array of environmental exposures and air pollutants that affect mental health during the life course. AIMS: We gather interdisciplinary expertise and knowledge across the air pollution and mental health fields. We seek to propose future research priorities and how to address them. METHOD: Through a rapid narrative review, we summarise the key scientific findings, knowledge gaps and methodological challenges. RESULTS: There is emerging evidence of associations between poor air quality, both indoors and outdoors, and poor mental health more generally, as well as specific mental disorders. Furthermore, pre-existing long-term conditions appear to deteriorate, requiring more healthcare. Evidence of critical periods for exposure among children and adolescents highlights the need for more longitudinal data as the basis of early preventive actions and policies. Particulate matter, including bioaerosols, are implicated, but form part of a complex exposome influenced by geography, deprivation, socioeconomic conditions and biological and individual vulnerabilities. Critical knowledge gaps need to be addressed to design interventions for mitigation and prevention, reflecting ever-changing sources of air pollution. The evidence base can inform and motivate multi-sector and interdisciplinary efforts of researchers, practitioners, policy makers, industry, community groups and campaigners to take informed action. CONCLUSIONS: There are knowledge gaps and a need for more research, for example, around bioaerosols exposure, indoor and outdoor pollution, urban design and impact on mental health over the life course.

Advances in sensing ammonia from agricultural sources.

Reducing ammonia emissions is one of the most difficult challenges for environmental regulators around the world. About 90% of ammonia in the atmosphere comes from agricultural sources, so that improving farm practices in order to reduce these emissions is a priority. Airborne ammonia is the key precursor for particulate matter (PM2.5) that impairs human health, and ammonia can contribute to excess nitrogen that causes eutrophication in water and biodiversity loss in plant ecosystems. Reductions in excess nitrogen (N) from ammonia are needed so that farms use N resources more efficiently and avoid unnecessary costs. To support the adoption of ammonia emission mitigation practices, new sensor developments are required to identify sources, individual contributions, to evaluate the effectiveness of controls, to monitor progress towards emission-reduction targets, and to develop incentives for behavioural change. There is specifically a need for sensitive, selective, robust and user-friendly sensors to monitor ammonia from livestock production and fertiliser application. Most currently-available sensors need specialists to set up, calibrate and maintain them, which creates issues with staffing and costs when monitoring large areas or when there is a need for high frequency sampling. This paper reports advances in monitoring airborne ammonia in agricultural areas. Selecting the right method of monitoring for each agricultural activity will provide critical data to identify and implement appropriate ammonia controls. Recent developments in chemo-resistive materials allow electrochemical sensing at room temperature, and new spectroscopic methods are sensitive enough to determine low concentrations in the order of parts per billion. However, these new methods still compromise selectivity and sensitivity due to the presence of ambient dust and other interferences, and are not yet suitable to be applied in agricultural monitoring. This review considers how ammonia measurements are made and applied, including the need for sensors that are suitable for routine monitoring by non-specialists. The review evaluates how monitoring information can be used for policies and regulations to mitigate ammonia emissions. The increasing concerns about ammonia emissions and the particular needs from the agriculture sector are addressed, giving an overview of the state-of-the-art and an outlook on future developments.

Respiratory hospital admission risk near large composting facilities.

BACKGROUND: Large-scale composting can release bioaerosols in elevated quantities, but there are few studies of health effects on nearby communities. METHODS: A cross-sectional ecological small area design was used to examine risk of respiratory hospital admissions within 2500m of all 148 English large-scale composting facilities in 2008-10. Statistical analyses used a random intercept Poisson regression model at Census Output Area (COA) level (mean population 310). Models were adjusted for age, sex, deprivation and tobacco sales. RESULTS: Analysing 34,963 respiratory hospital admissions in 4656 COAs within 250-2500m of a site, there were no significant trends using pre-defined distance bands of >250-750m, >750-1500m and >1500-2500m. Using a continuous measure of distance, there was a small non-statistically significant (p=0.054) association with total respiratory admissions corresponding to a 1.5% (95% CI: 0.0-2.9%) decrease in risk if moving from 251m to 501m. There were no significant associations for subgroups of respiratory infections, asthma or chronic obstructive pulmonary disease. CONCLUSION: This national study does not provide evidence for increased risks of respiratory hospital admissions in those living beyond 250m of an outdoor composting area perimeter. Further work using better measures of exposure and exploring associations with symptoms and disease prevalence, especially in vulnerable groups, is recommended to support regulatory approaches.

Sub-micrometer particle production by pressurized metered dose inhalers.

Evidence from both the air pollution and inhaled aerosol therapy fields suggests that the physiological impact of fine and ultrafine aerosols (defined as those below 1000 and 100 nm aerodynamic diameter, respectively) may be greater than their mass or volume of active agent alone might suggest. Traditionally, Andersen impactors and liquid impingers have been used for the sizing of particles produced by pressurized metered dose inhalers (pMDIs). However, these fail adequately to size particles in the ultrafine range (<100 nm aerodynamic diameter). In this paper, we report on a method of sizing pMDI particles down to 10 nm, using an electrical low pressure impactor (size range 30 nm to 10 microm) and a scanning mobility particle sizer (size range 3-150 nm). A range of pMDI drug formulations were assessed, including Flixotide (HFA-fluticasone propionate, GSK [Glaxo Smith Klein]), Salbulin (HFA-salbutamol sulphate, 3M), Qvar (HFA-beclomethasone dipropionate, 3M), Ventolin (HFA-salbutamol sulphate, GSK), Atrovent Forte (CFC-ipratropium bromide, Boehringer Ingelheim), Becotide (CFC-beclomethasone dipropionate, GSK), Pulmicort (CFC-budesonide, Astra Zeneca), and Serevent (CFC-Salmeterol xinafoate, GSK). All devices yielded high numbers of fine and ultrafine particles, with number median aerodynamic diameters (NMAD) of Qvar 68 nm, Becotide 73 nm, Salbulin 85 nm, and Pulmicort 89 nm, and %<100 nm Qvar 76%, Becotide 65%, Salbulin 61%, and Pulmicort 60%. We found a general trend of HFA-propelled pMDIs to produce smaller particles than the CFC units, but this trend was not statistically significant. These findings support previous published work, which suggests that significant bioactivity of pMDIs may reside in the ultrafine fraction.

Production of radioactive particles for use in environmental studies.

This paper presents an aerosol generation technique developed to produce dry aerosol particles of various sizes from aqueous solutions of salt. The technique was tested with sodium chloride, lithium carbonate and uranyl acetate at various aqueous concentrations which produced particles in the size range of 0.13-1.37 microm Mass Median Diameter (MMD). The generated aerosols were acceptably monodisperse with a geometric standard deviation of 1.4-2. Both MMD and Mass Median Aerodynamic Diameter (MMAD) increased significantly (p<0.001) with increased concentration of the salt in solution. The technique can also be used to generate aerosols of different chemical species. The results obtained indicate that the system is convenient for use with various aerosol-forming materials, with a stable particle size distribution being maintained for a long period of steady operation. The technique was successfully applied in wind tunnel studies to simulate the release of submicron radioactive particles and their interception by crops, grass and tree canopies. The relevance and application of the technique in other areas of environmental assessment studies is discussed.