Air Quality Index Trend

Overview

Air Quality Index (AQI) trend charts visualize air pollution levels over time with color-coded zones representing health impact categories. This pattern helps public health officials, citizens, and researchers track air quality changes and identify concerning periods.

When to use

Monitor daily or hourly air quality
Track pollution trends over weeks/months
Compare air quality across locations
Public health advisories and alerts
Environmental policy impact assessment

Not ideal

Single point-in-time measurement (use gauge instead)
Multiple pollutants without clear distinction
When pollutant composition matters more than aggregate AQI

Key variations

Different AQI standards (US EPA, China MEP, etc.)
Hourly vs daily aggregation
Color zones matching health categories
Multiple pollutants (PM2.5, PM10, O3, etc.) as separate series
Include dominant pollutant annotations

Use cases

Weather and news apps showing local air quality
Environmental agency dashboards
Public health campaigns
Urban planning and traffic management
Research on pollution sources and patterns
School/outdoor activity decision support

Data (CSV)

x,y
2014-06-01,55
2014-06-02,25
2014-06-03,56
2014-06-04,33
2014-06-05,42
2014-06-06,82
2014-06-07,74
2014-06-08,78
2014-06-09,267
2014-06-10,185
2014-06-11,39
2014-06-12,41
2014-06-13,64
2014-06-14,108
2014-06-15,147
2014-06-16,132
2014-06-17,133
2014-06-18,218
2014-06-19,206
2014-06-20,172
2014-06-21,145
2014-06-22,158
2014-06-23,178
2014-06-24,140
2014-06-25,109
2014-06-26,94
2014-06-27,51
2014-06-28,45
2014-06-29,33
2014-06-30,38
2014-07-01,46
2014-07-02,32
2014-07-03,26
2014-07-04,37
2014-07-05,41
2014-07-06,46
2014-07-07,38
2014-07-08,44
2014-07-09,40
2014-07-10,77
2014-07-11,86
2014-07-12,139
2014-07-13,101
2014-07-14,122
2014-07-15,92
2014-07-16,52
2014-07-17,63
2014-07-18,78
2014-07-19,85
2014-07-20,103

Performance tips

Use hourly data for real-time monitoring
Aggregate to daily for trend analysis
Color code zones in background for instant recognition
Add tooltips with pollutant details and health advice

FAQ

What AQI scale should I use? Depends on location. US EPA AQI (0-500) is common globally. China and India have their own scales. Always label which scale you're using.

Should I show specific pollutants? If space allows, show PM2.5 and O3 as they're often most relevant. Full breakdown works better in a table or separate chart.

How to handle missing data? Leave gaps. Don't interpolate AQI—it can change rapidly and missing data may indicate sensor issues.

What about historical comparison? Overlay previous year's data or show rolling averages to reveal trends vs seasonal variation.

Should zones be in the background or foreground? Background shading is traditional and keeps focus on the data line. Foreground segments work if line color itself changes by zone.

How to communicate health advice? Add subtitle or annotations during high AQI events with recommended actions (e.g., "Limit outdoor activity").

Can I show multiple cities? Yes, but use small multiples or separate series with clear labels. Overlaying many cities gets cluttered quickly.

Example

Guide