Figure 1From: Participatory testing and reporting in an environmental-justice community of Worcester, Massachusetts: a pilot project Time series of PM2.5. Plot of July 6 corresponds to Figure 2. Reference lines are NAAQS 24-h average standard (35 μ g/m3) and annual average (15 μ g/m3). While the sensor tends to overestimate actual levels - so direct comparisons with standards are inappropriate - the data may be a surrogate for actual levels.Back to article page