Which of the following is NOT one of the six criteria pollutants that may contaminate indoor spaces?

The correct answer is hydrogen peroxide, as it is not classified as one of the six criteria pollutants that are typically monitored for their potential impact on air quality and public health. The six criteria pollutants recognized by the Environmental Protection Agency (EPA) include carbon monoxide, lead, ozone, particulate matter, sulfur dioxide, and nitrogen dioxide. These pollutants are commonly linked to both outdoor and indoor environments and are regulated due to their harmful health effects and prevalence in various urban and environmental settings.

Hydrogen peroxide, while it can be a powerful oxidizing agent and is sometimes used as a disinfectant, does not fall under the category of criteria pollutants. It is not regularly monitored or regulated in the same way as the other listed pollutants.

The other pollutants mentioned—carbon monoxide, lead, and ozone—are significant in discussions of air quality, as they are known to have direct adverse effects on human health and the environment, making them important for consideration in both indoor and outdoor air quality management.