Reduktion der Feinstaubbelastung in Klassenräumen durch verbesserte Reinigung: Ausmaß der Belastung und Ergebnisse einer Pilotstudie in Bayern

Toxicity and elemental composition of particulate matter from outdoor and indoor air of elementary schools in Munich, Germany

Outdoor particulate matter (PM(10)) is associated with detrimental health effects. However, individual PM(10) exposure occurs mostly indoors. We therefore compared the toxic effects of classroom, outdoor, and residential PM(10). Indoor and outdoor PM(10) was collected from six schools in Munich during teaching hours and in six homes. Particles were analyzed by scanning electron microscopy and X-ray spectroscopy (EDX). Toxicity was evaluated in human primary keratinocytes, lung epithelial cells and after metabolic activation by several human cytochromes P450. We found that PM(10) concentrations during teaching hours were 5.6-times higher than outdoors (117 ± 48 μg/m(3) vs. 21 ± 15 μg/m(3), P < 0.001). Compared to outdoors, indoor PM contained more silicate (36% of particle number), organic (29%, probably originating from human skin), and Ca-carbonate particles (12%, probably originating from paper). Outdoor PM contained more Ca-sulfate particles (38%). Indoor PM at 6 μg/cm(2) (10 μg/ml) caused toxicity in keratinocytes and in cells expressing CYP2B6 and CYP3A4. Toxicity by CYP2B6 was abolished with the reactive oxygen species scavenger N-acetylcysteine. We concluded that outdoor PM(10) and indoor PM(10) from homes were devoid of toxicity. Indoor PM(10) was elevated, chemically different and toxicologically more active than outdoor PM(10). Whether the effects translate into a significant health risk needs to be determined. Until then, we suggest better ventilation as a sensible option.

PRACTICAL IMPLICATIONS

Indoor air PM(10) on an equal weight base is toxicologically more active than outdoor PM(10). In addition, indoor PM(10) concentrations are about six times higher than outdoor air. Thus, ventilation of classrooms with outdoor air will improve air quality and is likely to provide a health benefit. It is also easier than cleaning PM(10) from indoor air, which has proven to be tedious.

Levels and indoor-outdoor relationships of size-specific particulate matter in naturally ventilated Portuguese schools

Indoor exposure to particulate matter (PM) has received great interest due to the epidemiological evidence of its health impact, particularly in susceptible populations such as children. The present study investigated indoor concentrations of three PM size fractions in 11 naturally ventilated schools with static heating systems, and the relationship between indoor and outdoor PM concentrations. The study was performed in Porto, Portugal, during winter and included school buildings and individual classrooms with walk-through surveys, as well as indoor and outdoor air monitoring. Mean 12-h indoor daytime concentrations PM₁₀, PM(2.5), and PM₁ were 140, 95, and 91 μg/m³, respectively. During the day, PM(2.5) and PM₁ concentrations were lower indoors than outdoors (indoor/outdoor ratios of 0.83 and 0.8, respectively), whereas PM₁₀ showed the opposite trend. Concentrations decreased significantly during the night, 49% for PM₁₀ and 27% for PM(2.5) and PM₁. These findings reflect the significant contribution from the activities of occupants inside classrooms to higher indoor levels of PM₁₀ levels, whereas the fine fraction of PM(2.5) and PM₁ is primarily influenced by outdoor concentrations. This study provides a link between size-specific PM in Portuguese schools with contribution of outdoor versus indoor air. Our results suggest that exposure to PM is high and highlights the need for strategies that provide healthier school environments.