School bus pollution and changes in the air quality at schools: a case study

Area of Science:

• Environmental Science
• Public Health
• Atmospheric Chemistry

Background:

• Millions of US schoolchildren are exposed to traffic-related air pollutants.
• Diesel-powered school buses generate health-relevant ultrafine aerosols.
• Exposure is particularly high near schools with intense bus activity.

Purpose of the Study:

• To determine aerosol concentration and elemental composition near a US public school.
• To assess the impact of school bus traffic on local air quality.
• To quantify children's exposure to diesel exhaust particles.

Main Methods:

• Case study in a midwestern metropolitan area during two seasons (March and May).
• Real-time aerosol monitoring using particle size spectrometers and non-size-selective instruments.
• PM2.5 air sampling with Harvard Impactors for elemental analysis (XRF) and carbon content (thermal-optical transmittance).

Main Results:

• Particle number concentration at the school site was 2.2-4.7 times higher than at a control site.
• Higher concentrations of elemental carbon (2.8-3.1 times) were found at the school site.
• Aerosol particle counts correlated with school bus traffic intensity on some days.

Conclusions:

• School bus traffic significantly contributes to aerosol pollutant exposure in school vicinities.
• Diesel exhaust particles are a major component of this increased exposure.
• Findings highlight the need for strategies to mitigate air pollution exposure for schoolchildren.