Air Quality Data When Travelling Internationally: A Practical Guide

Checking air quality abroad is more complicated than it looks because the number on your app may be calculated using a completely different formula than the one you use at home. A reading of 75 in Beijing, 75 in Delhi, and 75 in Paris can represent three different actual pollution levels depending on which scale each city uses. This guide explains how international AQI systems differ, which apps give you reliable data by region, and how to make genuinely useful health decisions when the monitoring infrastructure varies widely between countries.

Why International AQI Numbers Are Not Directly Comparable

The Air Quality Index was developed by the US EPA as a domestic standard. Most countries have since created their own versions using different pollutant breakpoints, different averaging periods, and sometimes different pollutants entirely. The result is that the same numerical reading across two different national systems does not represent the same actual pollution exposure.

This creates a specific trap for travelers who check air quality on a global app without knowing which scale it is applying. Some apps normalize all readings to the US EPA scale, making comparisons meaningful. Others display the local national AQI, which looks like a familiar number but measures something different. The difference is not trivial. At a PM2.5 concentration of 35 micrograms per cubic meter, the US EPA would report an AQI of approximately 100 (the top of Moderate). China’s AQI formula would report approximately 75 for the same concentration. India’s AQI formula would report approximately 100 but using different averaging methods. Travelers who do not know which scale they are looking at may systematically underestimate or overestimate their actual exposure.

How Major Regional AQI Systems Differ

Understanding the key differences between regional systems lets you interpret any number you encounter with the right context.

United States: EPA AQI

The US EPA AQI runs from 0 to 500. A score of 100 corresponds exactly to the national ambient air quality standard for the worst pollutant measured at that moment. PM2.5 is calculated using a 24-hour average concentration. The Good range (0 to 50) corresponds to PM2.5 below roughly 12 micrograms per cubic meter. This is the baseline most international apps use when they claim to show a “standardized” AQI.

China: AQI (Guo Biao Standard)

China’s AQI also runs from 0 to 500 and uses the same six color categories as the US system, which makes the two look interchangeable. They are not. China’s PM2.5 breakpoints are set at higher concentrations per AQI unit, which means a Chinese AQI of 100 corresponds to a PM2.5 concentration higher than what the US EPA would report as AQI 100. A Chinese reading in the “Good” range (0 to 50) can correspond to PM2.5 levels that the US EPA would classify as Moderate. Travelers from the US or EU checking air quality in Chinese cities via apps that display the local AQI may underestimate their actual exposure. For major Chinese cities, the US Embassy and Consulates operate their own PM2.5 monitors and report data in US EPA AQI format at airnow.gov. This is the most reliable cross-comparable source for China.

India: National AQI

India’s National AQI runs from 0 to 500 with six categories broadly similar to the US system. However, it calculates the index using a 24-hour rolling average for most pollutants and incorporates a sub-index for eight pollutants rather than six. India’s Good range (0 to 50) and the US Good range (0 to 50) correspond to meaningfully different PM2.5 concentrations. Indian cities, particularly Delhi and Mumbai, regularly exceed AQI 300 on the Indian scale during winter months, which corresponds to hazardous readings on any international comparison. The Central Pollution Control Board (CPCB) publishes official data at cpcb.nic.in.

Europe: CAQI and EAQI

Europe uses two separate systems, which creates its own layer of confusion. The Common Air Quality Index (CAQI) runs from 0 to above 100, with no fixed upper bound, making direct numerical comparison to any 0-to-500 system impossible. The newer European Air Quality Index (EAQI), introduced by the European Environment Agency, uses a 0 to 100-plus scale with five bands. Neither maps cleanly onto US AQI numbers. A traveler who sees a CAQI of 50 in Paris is not looking at the same air quality as a US AQI of 50. The European Environment Agency publishes real-time EAQI data at airindex.eea.europa.eu, which is the most reliable source for EU countries.

WHO Global Air Quality Guidelines

The WHO’s 2021 Air Quality Guidelines set a stricter PM2.5 24-hour standard of 15 micrograms per cubic meter, tighter than what either the US EPA or most national agencies currently use as their “Good” threshold. The WHO guidelines do not produce a single AQI number but they provide a useful universal baseline: any location where PM2.5 regularly exceeds 15 micrograms per cubic meter is above WHO-recommended levels regardless of what the local AQI system calls it.

Which Apps and Sources to Use by Region

The app you use at home may give you unreliable or misformatted data in another country. The sources below are organized by region based on data coverage, update frequency, and whether they normalize to a consistent scale.

Region	Recommended Source	Scale Used	Notes
United States	AirNow.gov / AirNow app	US EPA AQI	Official EPA data. Hourly updates. Most reliable US source.
China	US Embassy Monitor (via AirNow or IQAir)	US EPA AQI	Use this over local apps for cross-comparable readings.
India	CPCB Sameer App / IQAir	India National AQI	IQAir converts to US EPA AQI for easier comparison.
Europe	airindex.eea.europa.eu / IQAir	EAQI / US EPA AQI	EEA site uses EAQI. IQAir normalizes to US EPA scale.
Southeast Asia	IQAir / AQICN.org	US EPA AQI (normalized)	Official monitoring varies by country. IQAir aggregates best available data.
Middle East / Africa	IQAir / OpenAQ	US EPA AQI (normalized)	Monitoring station density is lower. Use multiple sources and treat readings as estimates.
Global	IQAir AirVisual app	US EPA AQI (normalized)	Aggregates government and community sensors. Normalizes all readings to US EPA AQI for direct comparison.

IQAir’s AirVisual app is the most consistently reliable cross-border tool because it converts all readings to US EPA AQI format regardless of the local national standard, which eliminates the scale comparison problem. AQICN.org provides a useful backup for regions with sparse official monitoring. Neither source is perfectly accurate in areas where ground-level monitoring is limited, and both may rely on satellite estimates or community sensors rather than certified government instruments in those zones.

What to Do in Countries with Limited Monitoring Data

A significant portion of the world’s land area has sparse or no ground-level air quality monitoring. Large parts of sub-Saharan Africa, Central Asia, and rural Southeast Asia fall into this category. When official monitor data is unavailable or the nearest station is hundreds of kilometers away, travelers need alternative approaches.

• Use satellite-based PM2.5 estimates: NASA’s FIRMS platform and the World Air Quality Index project use satellite aerosol optical depth data to estimate surface PM2.5 in areas without ground monitors. These estimates carry higher uncertainty than direct measurements but are substantially better than nothing. AQICN.org incorporates satellite data in its global map views.
• Check visibility as a rough proxy: PM2.5 scatters light and reduces visibility. A clear day where you can see distant mountains or buildings typically indicates lower PM2.5 than a hazy day where visibility is below a few kilometers. This is not a calibrated measurement but it gives a directional sense when no data exists.
• Check local meteorological context: Dust storm seasons (common in the Sahel, Arabian Peninsula, and parts of South Asia), agricultural burning seasons (common in Southeast Asia from February through April), and dry season burning in Sub-Saharan Africa are predictable annual pollution events. Knowing the seasonal calendar for your destination lets you anticipate high-pollution periods even without real-time data.
• Use a portable personal monitor: Compact PM2.5 monitors from brands like IQAir, Laser Egg, and Atmotube provide real-time personal exposure readings. These are not government-certified instruments, but they give travelers a direct and portable measurement capability in locations where no public data exists.

Practical Steps for Sensitive Travelers

Travelers with asthma, COPD, cardiovascular disease, or other conditions that increase air quality sensitivity need a more structured approach than simply checking an app on arrival.

1. Research your destination’s typical AQI before booking: IQAir’s World Air Quality Report publishes annual rankings of cities and countries by average PM2.5. Checking a destination’s annual average and typical seasonal range tells you whether you are traveling to a chronically high-pollution environment or one where brief elevated periods are the main concern.
2. Identify your reliable data source before you land: Different apps work better in different countries. Know which app gives you US EPA-normalized readings for your specific destination before you need to make a health decision on the ground.
3. Pack your medications with travel buffer: High-pollution destinations can trigger increased rescue inhaler use. Packing one to two weeks of extra medication beyond your planned trip length avoids the problem of trying to source specific medications in a country where they may not be available under the same brand name or formulation.
4. Set a local action threshold before arrival: Decide in advance what AQI level will change your plans, whether that is skipping an outdoor market, moving a run indoors, or wearing a mask. Having a pre-decided number removes the in-the-moment guesswork when you are tired and jet-lagged.
5. Know what masks actually filter: N95 and KN95 masks filter PM2.5 effectively when fitted correctly. Surgical masks and cloth masks provide minimal PM2.5 protection. For travel to chronically high-pollution destinations, packing N95 masks for high-AQI days is a meaningful precaution. See AQI safety for sensitive groups for detailed guidance on condition-specific thresholds.

Common Mistakes Travelers Make with Air Quality Data

Even travelers who check air quality regularly make a few predictable errors when crossing into unfamiliar monitoring systems.

• Trusting a local app without checking which scale it uses: An app marketed in China showing AQI 80 is not equivalent to a US AQI of 80. Check the app’s methodology or switch to IQAir, which normalizes all readings to the US EPA scale, so you are always comparing like with like.
• Using a home-country app abroad: Apps calibrated for US data coverage (including the official AirNow app) show sparse or missing data outside the US. They may display “no data available” or fall back to low-resolution satellite estimates in regions without EPA-connected monitors. For destinations outside the US, use IQAir or AQICN.org instead.
• Checking once in the morning and assuming it holds all day: AQI in cities with heavy traffic peaks during commute hours. In countries near agricultural or industrial zones, burning often occurs at specific times of day or night. A single morning check can miss the worst part of the day by hours. Check every two to three hours during active outdoor time in unfamiliar environments.

Conclusion

Getting accurate air quality data abroad is a two-step process: find a source that normalizes readings to a consistent scale, and understand the seasonal and regional context that raw numbers can’t capture. IQAir’s AirVisual app covers both requirements for most destinations and is the single most practical tool for international travelers. For destinations with limited monitoring, combining satellite estimates with local meteorological knowledge and portable personal sensors gives a workable picture when official data is absent. Travelers with respiratory or cardiovascular conditions should prepare a destination-specific action plan before departure rather than making health decisions on the ground with unfamiliar tools. Read our guide on what is considered a good AQI to build a solid understanding of the US EPA scale before interpreting international readings against it.

Frequently Asked Questions