Scripted drives: A robust protocol for generating exposures to traffic-related air pollution

Area of Science:

• Environmental Health
• Exposure Science
• Transportation Studies

Background:

• Commuting in automobiles is a significant source of traffic-related air pollution (TRAP) exposure.
• Accurate measurement of in-vehicle TRAP exposure for health studies is difficult.
• Existing methods may not fully capture real-world commuting exposure dynamics.

Purpose of the Study:

• To develop and evaluate a robust scripted drive protocol for estimating real-world TRAP exposures during commutes.
• To assess the consistency and reliability of in-vehicle pollutant measurements using this protocol.
• To provide a standardized method for TRAP exposure assessment in health-related research.

Main Methods:

• A scripted drive protocol was implemented on the NJ Turnpike and local roads over 190 days (April 2007-October 2014).
• Participants were driven in a car with closed windows and open vents during morning rush hours.
• Real-time measurements of PM2.5, particle number concentration (PNC), carbon monoxide (CO), and black carbon (BC), plus integrated NO2 samples, were collected in the car cabin.

Main Results:

• Median in-cabin concentrations: 11 μg/m³ PM2.5, 40,000 particles/cm³ PNC, 0.3 ppm CO, 4 μg/m³ BC, and 20.6 ppb NO2.
• In-cabin concentrations were higher on the NJ Turnpike than local roads (e.g., 1.4x for PM2.5, 4x for BC).
• Ratios of concentrations proved more stable than absolute differences, showing robustness across various conditions except for PNC and PM2.5 trends.

Conclusions:

• Scripted drives offer a reliable method for generating consistent in-cabin exposure increments to TRAP.
• This protocol can enhance the accuracy of TRAP exposure assessment in epidemiological studies.
• Understanding in-vehicle pollutant dynamics is crucial for mitigating health risks associated with commuting.