During the 1st GO IAQS Index Breakpoints meeting, discussions focused on proposed breakpoints for various pollutants based on survey results, comparisons with existing standards, and feedback from attendees. The meeting aimed to cover results, compare them with existing breakpoints, and gather comments on specific pollutants, with a focus on PM2.5, Carbon Dioxide (CO2), Carbon Monoxide (CO), and Formaldehyde.
PM2.5 (Particulate Matter 2.5 microns)
Proposed Breakpoints: GO AQS decided on 5 micrograms per cubic meter (µg/m³) as the higher concentration for “good” air quality, derived from converting the WHO’s annual average into an index. Other instruments and country-oriented indexes typically consider upper limit 10 to 15 µg/m³ for “good” air quality. Professor Pawel Wargocki also recommended a maximum of 10 µg/m³ for the “good” tier using the Tail rating scheme.
Index Operation: The GO IAQS index is designed to update constantly based on real-time data from sensors, rather than hourly or as a 24-hour time-weighted average (TWA). This was a point of confusion for some attendees, as many original ambient indices (like EU and EPA) are based on TWAs over varying timeframes (e.g., 1-hour, 8-hour, 24-hour). The GO IAQS approach is to provide an immediate warning when a limit is exceeded.
Concerns/Discussions:
Time Frame: Attendees expressed a need for clarity on whether limits were immediate ceiling levels or TWAs, with some favoring immediate warnings for greater protection. One of the participants noted the public might be confused by treating standards that were originally TWAs as immediate warnings.
Sensor Accuracy: Sensor manufacturers worried that 5 µg/m³ is too low, as many low-cost sensors, especially those using infrared and laser detections, may not detect continuously or accurately in the 0-5 µg/m³ range (e.g., accuracy of +/- 3% in a 0-50 µg/m³ band).
Alert Frequency: Instantaneous alerts at boundary conditions (e.g., fluctuating around 15 µg/m³) could lead to frequent, unnecessary alerts. Manufacturers often roll out alerts less frequently (e.g., every 10 minutes) to avoid this.
Global Applicability: Achieving 0-5 µg/m³ is difficult in places with high air pollution like India and Bangladesh due to socio-economic reasons or environmental factors (e.g., open windows). This led to suggestions for an intermediate category (e.g., “very good” and “good”) to keep people motivated to improve air quality, recognizing that a very strict limit might be unachievable globally. The WHO 2021 standard guidelines offer multiple bands to allow countries to progressively improve.
Consistency: There was a call to clearly convey how GO AQS adapts referenced standards and calculation methods to avoid misunderstandings.
Conclusion: While GO AQS initially proposed 0-5 µg/m³ for the “good” tier, significant concerns were raised about its strictness, global applicability, sensor limitations, and the need to clearly communicate its real-time, immediate warning approach compared to traditional indices. The attendees acknowledged that 5 µg/m³ might be too strict for everyone.
Carbon Dioxide (CO2)
Proposed Breakpoints: The majority agreed with proposed limits of 400 to 800 parts per million (ppm) for “good” air quality, 800-1400 ppm for the second tier, and 1400-5000 ppm for the third tier. 800 ppm was identified as the predominant “higher concentration for good”. The upper limit for the Good tier aligns with Lidia Morawska’s paper Mandating indoor air quality for public buildings.
Comparisons: The European standard EN 13779 and Tail paper were referenced. Belgium uses 900 ppm generally, but 800 ppm when there’s an infection risk. Some suggestions included a stricter upper limit of 600 ppm for “good”.
Concerns/Discussions:
Purpose of CO2 Monitoring: Debate arose over whether CO2 levels are solely indicators of pathogen transmission or if they also impact cognitive decline and if they may help us avoid other indoor gas pollutants.
Immediate Warnings: Similar to PM2.5, concerns were raised about immediate warnings for CO2 due to numerical “bounce,” suggesting a brief exceedance requirement (e.g., 1-5 minutes) before an alert.
Legislation & Global Standards: Belgium’s existing legislation specifies 900 ppm, making an 800 ppm standard difficult to adopt without legal changes. The speaker acknowledged that GO AQS recommendations are not enforced but aim to influence.
Differentiated Approach: The idea of creating a differentiated index for epidemic/pandemic situations (requiring stricter limits) versus general conditions was discussed.
Conclusion: The proposed CO2 breakpoints received general agreement, but discussions highlighted the need for flexibility regarding regional regulations, the practicality of immediate alerts, and whether to differentiate standards based on health risks (e.g., epidemics).
Carbon Monoxide (CO)
Proposed Breakpoints: GO AQS proposed the discussion implied an upper limit for “good” around 5 ppm, with some recommending 3.49 or 3 ppm. Some suggested CO should only have “good” or “bad” breakpoints.
Comparisons: British standards were mentioned. The European work safety limit is 20 ppm, but GO AQS does not accommodate occupational limits.
Concerns/Discussions:
Health Impacts: A CO toxicologist highlighted over 100 epidemiological studies showing same-day mortality increases at CO levels as low as 1 ppm (8-hour average) or 2 ppm (1-hour average), suggesting that 3, 4, or 5 ppm are not safe long-term. Another participant also noted that low CO levels can have a hormetic beneficial response but agreed that “zero is optimal” might be too strong a statement.
Immediate Warnings: Again, a brief averaging time (a few minutes) was suggested before triggering an instant alarm for CO to avoid transient spikes.
Detector Types: Confusion arose over the comment “best handled by CO detectors connected to smoke detectors.” Albert clarified that standard CO alarms are regulated to only warn at very high thresholds (e.g., 70 ppm in US, 50 ppm in Europe) with significant time delays, which is not suitable for GO AQS’s immediate warning index. GO IAQS index is intended for monitors, not alarms.
Baseline Levels: A significant suggestion was to propose a limit based on a delta (difference) from the outdoor ambient background CO levels, as outdoor levels vary greatly globally (e.g., <1 ppm in America, ~10 ppm in Nigeria), and CO is not easily filterable. This would allow for a “good” indoor level relative to the local environment and acknowledge the benefits of a steady low background. However, it was noted that such a delta approach would be more challenging for legal enforcement and instrument implementation.
Conclusion: There was strong consensus to lower the upper limit for “good” CO levels from a potentially implied 5 ppm due to evidence of negative health impacts at very low concentrations. The concept of using a delta from outdoor ambient levels was proposed as a scientifically more correct, though legally and practically complex, approach.
Formaldehyde
Proposed Breakpoints: Proposed breakpoints were 0-50 parts per billion (ppb), 51-100 ppb, and 101-500 ppb. These numbers originated from the Building Biology Institute’s 2015 standard. The “Ultimate Tier” of GO AQS already has a specific limit of 27 ppb.
Comparisons: Some companies use higher occupational safety thresholds. A suggestion was made to set the max breakpoint for “good” at 8 ppb, following the TAIL scheme. The California Office of Environmental Health Hazard Assessment has a chronic reference exposure level of 9 micrograms per cubic meter (approximately 7.3 ppb) for 24/7 exposure, which was considered a more credible source for a “good level”.
Concerns/Discussions:
Long-term Effects: It was emphasized that dangerous effects of formaldehyde are not easily perceived in the short term but lead to serious long-term health issues, necessitating lower numbers for protection.
Source Credibility: A toxicologist questioned the credibility of the Building Biology Institute as an independent source, suggesting California’s chronic reference exposure level (around 7.3 ppb) as a more recognized and credible benchmark for a “good” 24/7 exposure level. Another participant concurred, recommending keeping the “good” category at around 7-9 ppb.
Conclusion: The proposed breakpoints of 0-50 ppb for “good” were discussed, but a strong recommendation emerged to lower the upper limit for “good” to around 7-9 ppb, aligning with more established and credible standards like California’s chronic reference exposure level, to reflect a safe 24/7 exposure.
General Conclusions
The GO IAQS index is designed to use real-time data from sensors and provide immediate warnings when thresholds are exceeded.
There’s a critical distinction between the “limits” set for pollutants and how the “index” communicates air quality, particularly regarding the use of immediate warnings versus traditional time-weighted averages.
Future versions of the standard may include submicron or ultrafine particles once more scientific data is available.
The discussions highlighted the challenge of creating a single global standard that is both protective of health and practically achievable across diverse socio-economic and environmental conditions.
The meeting ran out of time before discussing ozone, nitrogen dioxide and radon, which were planned for a future call.
GO AQS 
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