LONDON — Short-term exposure to indoor fine particulate matter may affect attention, memory, and autonomic nervous system activity in adults, according to new research published in iScience. The findings suggest that indoor air quality may have implications beyond physical health, although further research is needed to establish how the effects translate to real-world workplace productivity.

The randomized, single-blind crossover study included 90 working-age adults who completed cognitive assessments under two indoor air conditions. Researchers conducted the experiment in an environmentally controlled chamber at University College London in the United Kingdom. Each participant experienced both conditions, with sessions separated by a one-week washout period.

Researchers generated fine particulate matter (PM2.5) by burning unscented paraffin candles. In the higher-exposure condition, a portable air purifier operated with a sham filter. In the lower-exposure condition, the purifier used a high-efficiency particulate air (HEPA) filter.

Cognitive performance was assessed using a computer-based test battery covering memory, attention, perception, coordination, and reasoning. Researchers also measured heart rate variability (HRV) and electrodermal activity (EDA) to examine potential links between particulate exposure, autonomic nervous system responses and cognitive performance.

Participants performed better on several memory and attention tasks in the lower-PM2.5 condition. The differences included slower reaction times and lower accuracy on selected tasks during higher exposure. The researchers found no statistically significant differences in coordination or reasoning between the two conditions. Results in the perception domain were mixed.

Higher PM2.5 exposure was also associated with lower HRV during cognitive testing. Four HRV measures showed significant differences between conditions during testing, but not during the resting period before testing. Researchers found no significant differences between exposure conditions in the measured EDA indicators.

The authors said the findings add to evidence that short-term exposure to indoor PM2.5 can affect cognitive skills, particularly attention and memory. These effects could have implications for tasks that require sustained attention or quick decisions. However, the study did not directly assess job performance, workplace productivity, driving safety, or clinical impairment, so those outcomes cannot be concluded from the results.

The study also has limitations. Participants were healthy adults between 18 and 30 years old. Nearly all participants had a master’s degree or higher, limiting the extent to which the findings can be generalized to other populations. In addition, the researchers generated PM2.5 through candle combustion and did not conduct detailed chemical analysis of the particles. 

For HVACR contractors, the research highlights the potential relevance of indoor particulate matter control when discussing building air quality. Filtration and other IAQ strategies may help reduce occupants’ exposure to airborne particles, but the study does not establish specific equipment recommendations or quantify productivity gains from filtration. The authors called for further research involving broader age groups and additional real-world conditions to better understand the effects of short-term indoor PM2.5 exposure.