Always back up to multiple copies in multiple locations in multiple mediums!
And periodically test the discs watching for increases in correctable error rate - and make new copies before you start to get uncorrectable errors.
Coal smoke may also include particulate and other combustion products that can deposit on gear over time. That is because coal is not pure carbon - it contains other naturally occurring chemicals, and nitrogen is available from the combustion air. Note that acid rain is a byproduct of coal burning power plants. (https://www3.epa.gov/acidrain/what/
Whether or not it is a problem for you will depend in part on the concentration of the smoke and combustion products in the air. I suspect being near home fires and unregulated industrial plants may be the worst.