Indoor hydrogen peroxide derived from ozone/d-limonene reactions

Area of Science:

• Environmental Chemistry
• Indoor Air Quality

Background:

• Indoor environments can experience elevated ozone levels from outdoor smog or indoor sources.
• Volatile organic compounds like d-limonene are common indoors and react with ozone.

Purpose of the Study:

• To investigate the products of ozone and d-limonene reactions in a controlled indoor setting.
• To assess the impact of air exchange rates on pollutant concentrations and particle characteristics.

Main Methods:

• A pilot study was conducted in a controlled office environment simulating high ozone conditions.
• Reactions between ozone and d-limonene were monitored under varying air exchange rates (0.5-18 h⁻¹).
• Concentrations of hydroperoxides (including hydrogen peroxide, H2O2) and secondary organic aerosols (SOA) were measured.

Main Results:

• Ozone and d-limonene reactions produced hydroperoxides (1.0-1.5 ppb at low ventilation, 0.6-0.8 ppb at high ventilation) and SOA (10-100 μg m⁻³).
• Lower air exchange rates resulted in higher H2O2 and SOA concentrations.
• Reduced ventilation also shifted particle size distribution towards larger particles (0.3-0.7 μm diameter).

Conclusions:

• Indoor ozone-driven chemistry, particularly with d-limonene, generates H2O2 and SOA, increasing respiratory exposure risks.
• Lower indoor ventilation rates exacerbate the formation and accumulation of these hazardous indoor air pollutants.
• The co-occurrence of H2O2 with hygroscopic SOA facilitates its transport into the lower respiratory tract.