Lost in the concern over the Sterigenics plant near Smyrna is the fact that the plant is located less than a mile from Plant McDonough, site of millions of tons of toxic coal ash, much of it buried in unlined pits beneath ground water level. The exposure to carcinogens from both locations may be more threatening than the sum of the individual exposure to both.
In a process known as “synergism,” the combined effect of two toxic materials can be more deadly than the sum of the two. For example, if the ethylene oxide from Sterigenics is expected to cause an additional 10 cancers per year and the beryllium from the Plant McDonough site is expected to cause 10 additional cancers, the outcome for the affected population may be 25 or 30 or 40 additional cancers rather than the expected 20.
Unfortunately, our regulatory system only considers individual threats in isolation without considering synergistic effects. For those concerned about either the Sterigenics facility or the Plant McDonough coal ash dump, I recommend that you fight for the most stringent controls possible. The ethylene oxide from Sterigenics combined with the nasty milieu of toxic chemicals from the coal ash site makes it highly likely that there are synergistic effects doing their deadly work on the surrounding population.