This session served as a crucial follow-up to our initial discussion on environmental pollutants, as we previously ran out of time to cover all the necessary ground. In today’s meeting, we delved into the specifics of index breakpoints for ozone, nitrogen dioxide, and radon.

Ozone (O3)

Proposed GO IAQS Index: The proposed index tiers for ozone are 0 to 50 parts per billion (ppb) for “good,” 51 to 100 ppb for “moderate,” and 101 to 300 ppb or more for “unhealthy”.

Comparison and Concerns: This proposal aligns with the California Air Resources Board’s suggestion of 50 ppb, although one person suggested lowering the upper limit for “good” to 20 ppb. A significant concern raised was that ozone actively participates in chemical reactions indoors, potentially generating more harmful secondary pollutants like formaldehyde, making it preferable to provide the lowest possible value. It was also noted that devices, even fans, can accidentally generate ozone indoors.

“Instant Ceiling” vs. Time-Weighted Average: A member highlighted a critical distinction: GO IAQS Index proposes an “instant ceiling” for ozone, meaning the limit is a maximum at any given moment, unlike many other organizations (e.g., ambient space standards) that use time-weighted averages (e.g., 1-hour, 8-hour, 24-hour averages). This “instant ceiling” approach is intended to be more protective. However, members argued that if 50 ppb is adopted as a limit for continuous exposure (24/7, 365), it is “much too high” compared to what other organizations would set for such continuous limits, which would be significantly lower than their 8-hour averages.

Response/Conclusion: The idea of lowering the ozone value further will be considered for consistency.

Nitrogen Dioxide (NO2)

Proposed GO IAQS Index: The recommended index for NO2 is 0 to 30 ppb for “good,” 31 to 100 ppb for “moderate,” and 101 to 150 ppb or more for “unhealthy”.

Agreement and Concerns: This proposal largely received agreement, with no alternative values suggested. Concerns were noted regarding the formation of secondary pollutants from NO2’s reaction with VOCs. It was also pointed out that gas stoves can produce NO2 from partial combustion.

Consistency with Time-Weighted Averages: Similar to ozone, a member emphasized that if the proposed NO2 limit (e.g., 30 ppb for “good”) is presented as a continuous safe exposure level, it is “much less protective” than what other organizations would choose for a 24-hour or one-year average. The member noted that the WHO 2010 guidelines, which GO IAQS has adopted for limits, show a significant difference between 1-hour (106 ppb) and 8-hour (21 ppb) thresholds (approximately a five-fold difference). It was urged the group to be consistent, suggesting that if their index represents a continuous exposure, the limits should be much lower (e.g., by 2/3 or 3/4).

Conclusion/Next Steps: GO AQS acknowledged the need to reconsider and potentially lower the NO2 limits to be more strict or consistent with their existing adopted limits.

Radon (Rn)

Proposed Go IAQS Index: The proposed index for radon is 0 to 100 Becquerels per cubic meter (Bq/m³) for “good,” 101 to 200 Bq/m³ for “moderate,” and 201 Bq/m³ or more for “unhealthy”.

Nature of Radon and Comparisons: It was acknowledged that radon has no safe limit, and every level carries a risk. The proposed “good” limit of 100 Bq/m³ aligns with limits used by commercial companies and a group of scientists referenced TAIL. The SBM 2015 recommendations were stricter (e.g., 30 Bq/m³ for good).

“Action Level” vs. Annual Average: The U.S. EPA’s approach for radon is an “action level” that requires intervention as soon as it’s exceeded, which aligns with GO IAQS’s instantaneous approach. However, in the UK and Europe, radon limits are typically based on annual averages (e.g., 100 Bq/m³ domestic action level in the UK, varying limits across European countries like Greece’s 300 Bq/m³), and measuring annual averages indoors is challenging.

Practical Implications: High radon levels are common in Latin America, especially in airtight buildings, emphasizing the link between building airtightness and radon concentration. Ventilation is a key solution, and active subslab depressurization systems are considered the most energy-efficient for mitigation.

Concern: Setting the “good” limit at 100 Bq/m³ might lead building managers to only reduce radon to just below this threshold (e.g., 90 Bq/m³), rather than striving for lower, more protective levels (e.g., 50 or 20 Bq/m³).

Conclusion/Next Steps: The GO IAQS will include best practices for radon mitigation in their guidelines. The breakpoints for radon don’t need further tweaks.

Overall Conclusions and Future Considerations:

Air Quality “Score” Preferred: The consensus leaned towards using “Air Quality Score” over “Air Quality Index.” Participants found “score” more intuitive, clearer, and easier for the average person to understand, resembling a direct measure rather than a complex calculation. The term “subscores” could then refer to individual pollutant scores.

Emphasis on “Instant Ceiling”: A recurring theme was the GO IAQS’s intention to implement instantaneous limits (ceilings) for pollutants, a departure from the time-weighted averages common in other indices. While this is designed to be more protective, it necessitates careful consideration of the proposed numerical values, especially when compared to continuous exposure limits from other organizations.

Visual Scale and Terminology: Discussions also covered the visual representation of the score. The current scale, with 10 representing “good” quality and decreasing numbers for worse quality, was noted as potentially confusing by some, who are used to scales where higher numbers represent higher values (e.g., higher pollution). The reasoning for the current scale is that it represents “air quality” not “air pollution,” so higher numbers denote better quality. There was also a suggestion to refine the term “dominant pollutants” to “pollutants above their limits” or “warning level” to be more precise.

Adaptation and Clarity: The index/score will be translated into multiple languages and adapted for different regions, with consistent color schemes. The overall aim is to create an international index that effectively communicates indoor air quality and influences positive behavior change.

Recording: GO IAQS Breakpoints – 2nd Session

Next Step

The next crucial step in our project involves a comprehensive update to our white paper documentation. This phase is dedicated to meticulously incorporating all the valuable comments and suggestions gathered during the recent working group sessions. Our goal is to ensure the documentation accurately reflects the collective expertise and insights of the group, enhancing its clarity, accuracy, and completeness. This collaborative revision process is vital for producing a robust and well-vetted document that serves as a definitive guide for our project moving forward.