Volatile organic compounds (VOCs) are precursors for ozone formation. Although the major sources of VOC emissions are regulated, many areas in the United States seek further emissions reductions. As additional source categories are identified, regulations have focused more on consumer products. VOC emissions from consumer products, either applied outdoors or detrained outdoors from indoor applications, are believed to be an important anthropogenic VOC emissions source. Regulations are already in place limiting the reactivity, or ozone forming potential, of VOC content in consumer product formulations. These regulations may result in the substitution of some petrochemical solvents for biogenic solvents, due to their lower estimated reactivity. While this approach may help control localized outdoor air pollution issues, they may negatively impact indoor air quality.

This research examines the potential impacts of VOC consumer product regulations by focusing on d-limonene—a biogenic solvent with high estimated ozone forming reactivity. An orange was initially examined in an indoor environment, as it is the source for the d-limonene solvent. d-Limonene is then compared to a petrochemical solvent, both as in neat form and as an ingredient in a cleaning product formulation. These compounds and mixtures were injected into a chamber and cultured human epithelial lung cells were exposed to the gases and the particles, both before and after the chamber atmosphere was oxidized with ozone, as a means of estimating the potential indoor respiratory toxicity of the systems. The inflammation and cytotoxicity induced from these exposures were examined and dose-response curves were generated to assess the risk and policy management implications of such substitutions. Overall, the results showed that decreasing estimated ozone forming reactivity of pure solvents and cleaning product formulations containing these solvents do not reduce the potential toxicity to human lung cells. Therefore, regulations implemented to decrease outdoor exposure to air pollutants may be increasing health risks indoors.