Effects of elevated CO2 levels on lung immune response to organic dust and lipopolysaccaride

Abstract

Workplaces with elevated organic dust levels such as animal feed barns also commonly have elevated levels of gasses, such as CO2. Workers exposed to such complex environments often experience respiratory effects that may be due to a combination of respirable factors. We examined the effects of CO2 at the ASHRAE recommended limit (1000 ppm) as well as the EPA 8hr time weighted average limit (5000 ppm) on lung innate immune responses in mice with exposure to inflammatory lipopolysaccharide and organic dust. Mice were nasally instilled with dust extracts or LPS and immediately put into chambers with a constant flow of room air (approx. 430 ppm CO2), 1000 ppm, or 5000 ppm CO2 enriched air. Organic dust exposures tended to show decreased inflammatory responses with 1000 ppm CO2 and increased responses at 5000 ppm CO2. Conversely, LPS with addition of CO2 as low as 1000 ppm tended to inhibit several inflammatory markers. In most cases saline treated animals showed few changes with CO2 exposure, though some changes in mRNA levels were present. This shows that CO2 as low as 1000 ppm CO2 was capable of altering innate immune responses to both LPS and organic dust extracts, but each response was altered in a different fashion.