Rtuffli: SIGNAL publish from draft v137

2026-05-30T18:46:42Z

SIGNAL publish from draft v137

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{| class="wikitable" style="float:right; clear:right; margin:0 0 1em 1em; width:320px;"
|+ SIGNAL Earth Structured Data
|-
! Object type
| Damage Signal
|-
! SIGNAL Earth ID
| DS-00099
|-
! Observable type
| Person-days of PM2.5 exposure above threshold
|-
! Unit
| person-days (person-days)
|-
! Temporal structure
| Annual
|-
! Monitoring backbone
| —
|}


{{SignalTerm|type=DS|id=DS-00099|label=Person-days of PM2.5 Exposure Above Threshold}} is an environmental damage signal quantifying the cumulative duration and population affected by fine particulate matter (PM2.5) concentrations exceeding a defined health-based threshold. This metric integrates both the number of individuals exposed and the length of exposure, providing a comprehensive measure of population-level air pollution impact. PM2.5, airborne particles with diameters less than 2.5 micrometers, are known to penetrate deep into the respiratory system and are associated with adverse health outcomes including respiratory and cardiovascular diseases. Understanding the extent of population exposure to elevated PM2.5 levels is critical for assessing public health risks and informing environmental health research. The signal is expressed in person-days, representing the product of the number of people exposed and the number of days exposure exceeds the threshold within a given year.

== Geographic / System Context ==
This signal applies globally, encompassing diverse geographic regions with varying air quality profiles and population densities. PM2.5 concentrations and exposure levels differ widely between urban, suburban, and rural areas due to factors such as industrial activity, traffic emissions, biomass burning, and meteorological conditions. Population-weighted exposure accounts for the spatial distribution of inhabitants, emphasizing regions where large numbers of people experience elevated PM2.5. Consequently, the signal reflects both the environmental conditions and demographic patterns that influence human exposure to fine particulate pollution worldwide.

== Monitoring and Measurement ==
Monitoring of PM2.5 exposure relies on a combination of ground-based air quality measurement networks, satellite remote sensing, and atmospheric chemical transport models. Institutions such as the [https://en.wikipedia.org/wiki/National_Oceanic_and_Atmospheric_Administration NOAA], [https://en.wikipedia.org/wiki/National_Aeronautics_and_Space_Administration NASA], and various national environmental agencies contribute data and modeling expertise. Population data are integrated from census and demographic sources to weight exposure estimates. The annual aggregation of person-days above threshold involves calculating daily PM2.5 concentrations, identifying exceedance days relative to health-based standards, and multiplying by the exposed population for each geographic unit. This approach enables consistent and comparable assessment of exposure burdens across regions and time periods.

Within the SIGNAL system, this phenomenon is treated as a defined environmental signal whose boundaries and measurement conventions are described below.

== Signal Definition ==
{{SignalTerm|type=DS|id=DS-00099|label=Person-days of PM2.5 exposure above threshold}} quantifies the total number of person-days during which population-weighted PM2.5 concentrations exceed a specified health-relevant threshold within a calendar year. It represents a receptor-level impact in the human health domain, combining temporal and demographic dimensions to capture cumulative exposure burden.

== Boundary Conditions ==
Boundary inclusions encompass all geographic areas with available PM2.5 concentration data and corresponding population counts, aggregated at spatial scales sufficient to represent population distribution accurately. Exposure days are counted only when PM2.5 levels surpass the defined threshold, typically aligned with air quality guidelines or health-based standards. Boundary exclusions include regions lacking reliable air quality or population data, days with PM2.5 concentrations below the threshold, and exposure to particulate matter sizes other than PM2.5. The signal does not account for individual susceptibility or indoor air pollution sources.

== Aggregation Semantics ==
Geographic aggregation involves summing person-days across spatial units weighted by population distribution to produce regional, national, or global estimates. Temporal aggregation is annual, reflecting cumulative exposure over a calendar year. Cross-signal aggregation is not specified for this signal, as it focuses on a single chemical stressor and receptor impact. Aggregation methods emphasize consistency in spatial and temporal resolution to enable meaningful comparisons and trend analyses over time and across regions.

== Observational Status ==
Current monitoring infrastructure provides extensive data on PM2.5 concentrations and population distributions, supporting robust estimation of this signal at global and regional scales. However, data gaps remain in some low-resource or remote areas. Future SIGNAL releases may incorporate improved spatial resolution, refined exposure thresholds based on emerging health evidence, and integration with other air pollution and health impact signals to provide a more comprehensive assessment of environmental health risks.

== Related Signals ==
* None specified


== Key Associated People ==
* '''Z. Y. Chen''' (-) [Lead author]



== Sources ==
* [https://www.nature.com/articles/s41467-024-46103-3 Population exposure to multiple air pollutants and its compound episodes in Europe — 2024]

Person-days of PM2.5 Exposure Above Threshold - Revision history

Rtuffli: SIGNAL publish from draft v137