Background: The US is the third leading cotton-producing country worldwide and cotton farming is common in Georgia. Cotton harvest could be one of the significant contributors to particulate matter (PM) and bioaerosols. The use of respirators or masks is one of the most viable options for reducing dust and bioaerosol exposures among farmers. Unfortunately, the OSHA Respiratory Protection Standard (29 CFR Part 1910.134) does not apply to agricultural workplaces and filtration efficiency of commonly used N95 masks was never field-tested against airborne PM, microorganisms, and antibiotic resistance genes (ARGs) during cotton harvesting. This pilot study addressed these knowledge gaps.

Methodology: Two models of N95 facepiece respirators (cup-shaped and pleated) were evaluated for their protections against PM (PM₁, PM_2.5, and PM₁₀), culturable bacteria and molds, and ARGs in three cotton farms during cotton harvesting. Respirators were donned on a manikin head and penetrations of the above-mentioned contaminants were tested at 100L/min air flow rates. Mass concentrations of PM were measured by a DustTrak™ II Aerosol Monitor and culturable microorganisms were estimated by an SAS Super 100 Air Sampler. Genomic DNA was extracted from air samples using PowerSoil® DNA Isolation Kit. A series of comparative critical threshold (2^−ΔΔCT) real-time PCR was used to quantify targeted bacterial (16S rRNA genes), mold (ITS gene), and major ARGs.

Results: We found that penetrations of all three PM categories and culturable bacteria exceeded 5% in all experiments for both models of N95 respirators. Similar findings were observed for culturable molds except for two cases. The pleated model provided better protection for molds. Penetration levels of ARGs were >5% in most cases and the highest abundance and penetration was observed for phenicol.

Conclusions: In typical wearing conditions, N95 respirators did not provide desirable >95% protections against tested PM, culturable microorganisms, and ARGs during cotton harvesting works.