Crowd Sourcing of Environmental Data Act of 2021 This bill authorizes states to monitor certain criteria air pollutants (i.e., lead, ozone, particulate matter, or sulfur dioxide) by greatly increasing the number of air quality sensors under their state implementation plans. The Environmental Protection Agency (1) may not enforce a requirement concerning the method of monitoring if the derived data meets quality standards, and (2) must allow states to consider data derived from such methods when determining whether national ambient air quality standards for criteria air pollutants were exceeded.