Here's a fun one anyone could start on.
Traditionally, air pollution is measured by expensive, stationary and complex air-monitoring instrumentation. Only a few organizations, like Federal, State and some industries, typically collect data of such high quality. Even so, this limits the amount of environmental monitoring data that is often available for exposure and health assessments. As air quality management problems become more complex, there is a need for enhanced air quality and exposure monitoring capabilities.
To meet this growing technological need, EPA, the commercial sensor industry, academic institutions, and others, are developing, evaluating and applying a variety of innovative technologies.
Sample Links to some sensors
A sample Seeduino Air Quality box