Associations between Acute Exposures to PM 2.5 and Carbon Dioxide Indoors and Cognitive Function in Office Workers: A Multicountry Longitudinal Prospective Observational Study.
Level 3 - non-randomized controlled study
Prospective observational longitudinal cohort study
PubMed 35330988 · doi:10.1088/1748-9326/ac1bd8
What was done
A 12-month prospective observational longitudinal study evaluated 302 office workers in commercial buildings across six countries (China, India, Mexico, Thailand, the United States, and the United Kingdom). Real-time indoor concentrations of fine particulate matter (PM2.5) and carbon dioxide (CO2) were measured. Cognitive performance was evaluated via a mobile research application using the Stroop color-word test and an Addition-Subtraction (ADD) test.
What was found
Higher PM2.5 and CO2 levels were associated with slower response times and reduced accuracy for 8 out of 10 test metrics. Each interquartile range (IQR) increase in PM2.5 (IQR = 8.8 µg/m³) was associated with a 0.82% (95% CI: 0.42, 1.21) increase in Stroop response time, a 6.18% (95% CI: 2.08, 10.3) increase in Stroop interference time, a 0.7% (95% CI: -1.38, -0.01) decrease in Stroop throughput, and a 1.51% (95% CI: -2.65, -0.37) decrease in ADD throughput, with PM2.5 associations significant in 4 of 5 metrics only above 12 µg/m³. For CO2, an IQR increase (IQR = 315 ppm) was associated with a 0.85% (95% CI: 0.32, 1.39) increase in Stroop response time, a 7.88% (95% CI: 2.08, 13.86) increase in Stroop interference time, a 1.32% (95% CI: -2.3, -0.38) decrease in Stroop throughput, and a 1.13% (95% CI: 0.18, 2.11) increase in ADD response time.
Why it matters
The study provides international observational evidence that routine indoor exposure to elevated PM2.5 and reduced ventilation (elevated CO2) acutely impairs cognitive processing speed and accuracy in office workers.
Limits
As an observational study, it cannot establish direct causality. Potential confounders such as noise, temperature, humidity, lighting, work stress, and sleep were not reported in the abstract. Cognitive function was measured using only two app-based tests (Stroop and ADD), which may not reflect overall workplace performance.
Cited by
- contradicts Adverse effects from indoor carbon dioxide levels primarily occur at concentrations of 2,000 to 3,000 parts per million, whereas levels around 1,200 to 1,300 ppm are common and generally not severely problematic.