1. Review previous research and exposure standards for environmental and workplace exposure to "simple" or "nuisance" dust, particulate matter (PM10, PM4, PM2.5, and "respirable" dust particles), and crystalline silica (quartz).
2. Record GPS coordinates, wind speed and direction, particulate matter (mass concentration and particle concentration), and crystalline silica concentration, and photograph locations surrounding the EOG Resources Chippewa Falls sand processing plant before and during operation.
3. Report measured particulate matter and crystalline silica concentrations and recommended exposure standards to the Wisconsin Department of Natural Resources, EOG Resources, concerned citizens, and the environmental health community (through conference presentations and peer-reviewed publications).
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Research Questions
This research generates data from an on-campus fine particulate (PM2.5) monitor to assess air quality as the new student center is being built. Data from 11 additional monitors around, and one onsite at the EOG sand processing plant in Chippewa Falls are also analyzed, to answer the following questions:
1) Are particulate pollution levels generated from student center construction above the EPA 35 ?g/m3 24-hour or 15 ?g/m3 annual standards?
2) Are particulate levels at the sand plant site above these EPA levels?
3) Are crystalline silica levels at the sand plant site above a nominal 3 ug/m3 exposure standard?
This study benefits from collaboration of UW-Eau Claire faculty and students with the Concerned Chippewa Citizens community group and the Wisconsin Department of Natural Resources.
Research Answers
Initial sampling at the UW-Eau Claire student center construction site has found average 24-hour PM 2.5 levels that are below the EPA standard:
Using expected emission rates from the Chippewa Falls EOG sand plant (but not including background levels or fugitive dust emissions), the EPA-recognized SCREEN3 model predicted PM 10 concentrations lower than the 150 ug/m3 EPA standard:
A map showing the distribution of modeled PM10 particulate matter concentrations from the Chippewa Falls sand processing plant. The diagram was created using, SCREEN3, an EPA recognized modeling software. There are four zones with estimated particulate matter concentrations, numbered accordingly. Zone 1 has a particulate matter concentration of 24.27 µg/m3, zone 2 is 19.62 µg/m3, zone 3 is 14.25 µg/m3, and zone 4 is 10.98 µg/m3.
RESULTS FROM JULY 2011 SAMPLING
We'd like to share with you the air sampling data we collected on July 30 and 31, 2011 around the Chippewa Falls, Wisconsin EOG sand processing plant. These are considered "background" samples because the plant is not yet in operation (image: The Save the Hills Alliance):
On each day – Saturday July 30 and Sunday July 31, we collected temperature, relative humidity, wind speed and direction, and airborne particulate and crystalline silica concentration data. Sampling took place between 11 am and 7 pm. We chose an upwind location to the south south-west of the plant and two downwind locations to the north north-east of the plant, with landowner permission, for the sampling sites.
Our four eight-hour crystalline silica samples, two taken on July 30 and two taken on July 31, one upwind and one downwind each day, were analyzed by the Wisconsin Occupational Health Laboratory. All four samples found that silica levels were below the detection limit of 10 micrograms per sample, or 12 micrograms per cubic meter.
Here is an example of this equipment used to measure airborne respirable crystalline silica (image: SKC.com):
Respirable particle sizes are those 4 micrometers and smaller, called "PM 4." Our five-minute respirable particulate mass samples taken with the DustTrak instrument showed a slight increase of downwind dust concentration of 27 micrograms per cubic meter compared to an upwind concentration of 22 micrograms per cubic meter on July 30. On July 31, the up- and downwind concentrations were about the same, at 17 and 15 micrograms per cubic meter, respectively. The difference between days may have been due to greater wind speed of 2.4 meters per second on July 30 and 0.35 meters per second on July 31.
We can roughly compare the PM 4 respirable particles to the PM 2.5 size category. EPA has set a 24-hour standard for PM 2.5 of 35 micrograms per cubic meter; our measurements of PM 4 were below this level. We would like to emphasize that these five-minute samples only provide a very limited "snapshot" of conditions. To fully assess airborne particulate concentrations, long-term monitoring on the order of months to years is needed.We also collected eight-hour samples of particulates using our Dylos particle counter, finding that levels in the 0.5 to 2.5 micrometer size range were about four times higher on the second day, when we sampled downwind, compared to the first day upwind sample. The downwind sample averaged 248,000 compared to the upwind sample of 65,200 particles per cubic foot. These would roughly correspond to PM 2.5 levels of 24.8 micrograms per cubic meter downwind and 6.52 micrograms per cubic meter upwind, both below the 35 micrograms per cubic meter EPA standard.
To summarize our findings, in our two-day "snapshot" sampling upwind and downwind of the EOG Chippewa Falls sand plant before the plant began operation, we found:
- Airborne crystalline silica levels were below a detection limit of 12 micrograms per cubic meter.
- The five-minute DustTrak particulate mass samples found that respirable particulates up- and downwind were about the same on both days, and were below a relevant EPA standard.
- The eight-hour Dylos particulate count samples showed a four-fold higher level of particulates downwind (on the second day) compared to upwind (the first day).
- The particle measurement range from the DustTrak (15–27 micrograms per cubic meter) was similar to that from the Dylos instrument (6.5–25 micrograms per cubic meter). Both of these ranges are lower than the relevant EPA standard of 35 micrograms per cubic meter.
Our next planned sample collection will be in November 2011 after the sand processing plant begins operation.
