Public Lab Research note

Rising PM 2.5 in St James

by tylerknight | June 01, 2022 20:52 01 Jun 20:52 | #31003 | #31003

Another month of data, another month observing high PM 2.5 events in St James Parish.

Last month we reported data from March to April from the three Public Lab Air Monitors around St James. This month, we have more data from April to May, including a long, elevated event starting the day before Mother's Day, and continuing for five consecutive days. As always, you can continue to track PM 2.5 from our deployed Purple Air monitors from the Purple Air Map.

Table 1. Summary of Data from Three Public Lab Air Monitors April to May

Site # of Days Average PM 2.5 (μg/m3)
Maximum PM 2.5 (μg/m3)
Amount of Time over 12 μg/m3 (hrs)
% of Month over 12 μg/m3
30.3 %

St James
25.4 %

17.5 %

Similar to last month, the average PM 2.5 at all three sites over a 30-day period was less than 12 μg/m3. A reminder, 12 μg/m3 is the EPA annual standard for PM2.5 exposure, while 35 μg/m3 is the 24-hour standard. The average PM 2.5 at all three sites rose compared to the previous month, with Vacherie again showing the highest average of 9.26 μg/m3. This is a disturbing trend, as the average creeps ever higher, exposure increases and the air becomes unhealthier to breathe.

Also like last month, a significant amount of cumulative time at each site had concentrations above 12 μg/m3 - 9.3 days at Vacherie, 7.8 days at St James, and 5.3 days at Welcome. While no spikes were observed as high as those seen in the previous month, with maximum concentrations at all three sites seen around 50 μg/m3, there were more spikes above 12 μg/m3 overall compared to last month.

Figure 1. PM 2.5 at Vacherie from 4/24/2022 to 5/24/2022
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Figure 2. PM 2.5 at St James from 4/24/2022 to 5/24/2022
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Figure 3. PM 2.5 at Welcome from 4/24/2022 to 5/24/2022
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The length of high PM 2.5 events also increased. Last month, the longest elevated event was around 19 hours. This month, however, PM 2.5 concentrations started climbing on May 8th and lasted until May 13th. While the more than five days of concentrations over 12 μg/m3 doesn't exceed the annual standard, that's a troubling amount of time to be exposed to high concentration PM 2.5. On May 8th, a community member reported visible smoke from many plants in the area, including from Nucor Steel and Mosaic Fertilizer, which could be potential sources of particulate matter emissions during this event.

Both increasing average PM 2.5 and increasing duration of elevated events is a concerning trend to see. We will continue to monitor the data for trends, and encourage anyone who notices visible emissions or elevated concentrations of PM 2.5 to reach out with their observations.


Thank you for sharing updates on this project! Is the team planning to highlight specific times when you received community reports of odors or plumes on the timeseries graphs? It could be useful to see if the reports coincided with high readings.

One other suggestion is to consider displaying the "Amount of Time over 12 μg/m3" as a percentage of the monitoring period.

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Great ideas! I'll add a percentage column to the table to better highlight how much of the month was over 12 μg/m3.

Highlighting community reports is a good idea as well. Other than the main report during the 5-day period, we haven't received many direct observations unfortunately.

This is a good opportunity to remind the community to reach out to us with any observations of odors and visible plumes! You can make a post here on Public Lab, or add your observation to a public Google Sheets document!

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