Why did DEQ monitor air quality near Cascade Steel Rolling Mills?
Cascade Steel Rolling Mills was called in to the Cleaner Air Oregon program in February 2022, triggering a requirement that the facility report emissions from the factory. However, the Emissions Inventory the facility submitted assumed the presence of pollution control devices and modifications to existing equipment that the facility does not presently have. These proposed changes to existing conditions at the facility were not previously discussed with, or approved by, DEQ. Because conditions represented in the Emissions Inventory differed so substantially from the actual facility configurations, DEQ performed preliminary modeling of the underlying emissions data provided by the facility. Results showed the potential for elevated levels of metals in the air surrounding the facility when certain weather conditions exist. Because of these concerning results, DEQ placed an air monitor near the facility and began sampling in August 2022 to gain a better understanding of the current levels of metals in the air. Sampling was paused after Oct. 13, 2022 and later resumed on Dec. 14, 2022. This pause was to allow sampling of different seasonal weather conditions, which have the potential to impact the air quality data obtained from the current monitoring location.
What did the monitoring find?
DEQ sampled at a location just north of the facility boundary from Aug. 18 to Oct. 13. Sampling resumed on Dec. 14, 2022 and continued through Feb. 17, 2023. Generally, the monitoring showed levels of metals lower than the preliminary modeling predicted. However, on three separate days, the level of manganese monitored in the air exceeded its acute (24-hour exposure) Ambient Benchmark Concentration[1]. This occurred on Sept. 27, Dec. 29, and Jan. 5. In addition to this, lead was also found to be above its acute Ambient Benchmark Concentration on Jan. 5 as well. There were no other metals found to be above their respective acute Ambient Benchmark Concentration value.
Unlike most other days DEQ sampled, the wind on Sept. 27, Dec. 29, and Jan. 5 was blowing from the southwest, which is more typical of winter weather patterns. This wind direction aligns with when one would expect to see impacts at the monitor from the facility, meaning emissions blew from the facility towards the monitor. This indicates the potential for localized instances of elevated levels of metals, depending on weather conditions.
[1] - The Ambient Benchmark Concentration is the level at which a person breathing the contaminant may have an increased risk of health impacts. It does not mean that health effects will necessarily occur.
What does this mean for my health? High enough levels of manganese and lead exposure during infant and child development can affect their brain function. DEQ and Oregon Health Authority do not expect that the levels of manganese observed on Jan. 5, 2023, the highest values observed, are high enough to affect the neurodevelopment of an infant or child who spent time near the monitoring site that day. This is due to health protective assumptions used when setting an Ambient Benchmark Concentration and the limited extent of the exceedance monitored on Jan. 5. There is no safe level of lead, but the Ambient Benchmark Concentration for lead is set to minimize potential health effects.
However, monitoring results only represent a snapshot in time at one location. Data from one monitoring location over a short timespan are not sufficient to draw conclusions about the potential risk from facility emissions to people who live, work or congregate near the facility more generally.
Next steps DEQ has completed sampling near the facility and will continue to evaluate the cumulative impact of the facility's emissions on neighbors' health through the Cleaner Air Oregon risk assessment process.