Air Pollution inside Vehicles: Making a Bad Situation Worse

Area of Science:

• Environmental Health
• Public Health
• Tobacco Control Research

Background:

• Thailand has made progress in tobacco control, implementing smoke-free public places under the WHO Framework Convention on Tobacco Control (FCTC).
• Concerns exist regarding air pollution from particulate matter (PM2.5), particularly secondhand smoke (SHS) exposure within vehicles.
• Children and youth are especially vulnerable to the adverse effects of SHS.

Purpose of the Study:

• To measure secondhand smoke (SHS) levels, specifically PM2.5, inside typical Thai vehicles.
• To assess the impact of different ventilation and air conditioning conditions on indoor air quality.
• To provide evidence for policy development regarding smoking in vehicles in Thailand.

Main Methods:

• An experimental study was conducted in 10 common Thai vehicles (sedans, pickup trucks).
• Real-time air monitoring instruments measured PM2.5 concentrations over 20-minute intervals.
• Measurements were taken under four conditions, including variations in air exchange and air conditioning (AC) use, with monitoring in front and back seats.

Main Results:

• Mean PM2.5 levels in vehicles were substantially higher than WHO guidelines.
• Exposure levels reached 49 μg/m³ (back seat) and 72 μg/m³ (front seat), which are approximately 3 and 5 times the WHO 24-hour standard (15 μg/m³).
• The most common condition (all windows closed with AC/fan) resulted in the highest exposure levels.

Conclusions:

• Vehicle smoking in Thailand leads to dangerously high levels of secondhand smoke (SHS) exposure.
• Current ventilation practices in tropical climates exacerbate indoor PM2.5 concentrations.
• Urgent policy interventions are recommended to prohibit smoking in vehicles to safeguard public health.