An intervention study of PM2.5 concentrations measured in domestic kitchens

Exposures to elevated concentrations of fine particulate matter with diameter ≤2.5µm (PM2.5) are linked to multiple acute and chronic health effects, including increased risk of cardiovascular and respiratory disease. As people spend up to 70% in their own homes, exposures to pollutants indoors could have a greater impact on health than exposure outdoors. Cooking is a primary emission source of PM2.5 in dwellings, and is of interest as it is an activity conducted several times a day in most households. Therefore, occupants are at risk of exposure to elevated levels of PM2.5 emitted during cooking if these particles are not removed at source. This is particularly important in high occupancy dwellings, such as student housing, where cooking periods are likely to be longer or more frequent than average. 
We studied the changes between PM2.5 concentrations measured during two one-week periods in the kitchens of non-smoking, high occupancy dwellings in Nottingham, UK. The dwellings were occupied by students and there were between 2 and 6 occupants per household. The measurements were made during the heating season between 2016 and 2018. 
During the first week, temporal changes in PM2.5 concentrations were measured and the occupants of the dwellings were only informed that air quality parameters were being monitored, and so this period represents typical occupant behaviour. Before the second week of monitoring, the same occupants were shown the measured concentrations from week 1 and informed of the potential risks to their health that elevated PM2.5 concentrations may pose. Occupants recorded details of cooking activity throughout both weeks. 
During week 2 the occupants were also asked to make any intervention that they felt was appropriate, such as activating a range hood or opening a window or door. Specific guidance was not given and so this represents changes made by non-experts and may also indicate the approaches used by much of the population. 
The concentrations recorded during each period were investigated independently, and compared to assess whether simple interventions are effective in reducing PM2.5 concentrations due to cooking and if expert guidance and mitigation measures are required. The results suggest PM2.5 concentrations in student housing in the UK are high. Across all houses, measured concentrations exceeded the WHO daily mean threshold (25µg/m3) at least 14% of the time for Week 1, and 10% for Week 2. However, behavioural intervention was only found to reduce concentrations in one of the five houses investigated. This highlights the limitation of outsourcing ventilation decisions to non-experts, and automated ventilation systems should be considered.