• Legionella pneumophila as a Health Hazard to Miners: A Pilot Study of Water Quality and QMRA

      Madera-García, Valerie; Mraz, Alexis L.; López-Gálvez, Nicolás; Weir, Mark H.; Werner, James; Beamer, Paloma I.; Verhougstraete, Marc P.; Univ Arizona, Mel & Enid Zuckerman Coll Publ Hlth, Dept Commun Environm & Policy (MDPI, 2019-08)
      Legionella pneumophila (L. pneumophila), the causative agent of legionellosis, is an aquatic bacterium that grows in warm water. Humans are only presented with a health risk when aerosolized water containing L. pneumophila is inhaled. In mining operations, aerosolized water is used as dust control and as part of the drilling operations, a currently ignored exposure route. This study characterized L. pneumophila concentrations in the mine's non-potable water and the relationship between L. pneumophila and chlorine concentrations. These concentrations informed a quantitative microbial risk assessment (QMRA) model to estimate the infection risk to miners exposed to aerosolized water containing L. pneumophila. Fourteen water samples were collected from seven locations at a mine and analyzed for temperature, pH, chlorine, and L. pneumophila serogroup. Most samples (93%) tested positive for L. pneumophila cells. The faucet from the sprinkler system on the adit level (entrance to the underground mine levels) showed the highest concentration of L. pneumophila (8.35 x 10(4) MPN/L). Disability adjusted life years (DALYs) were estimated in the QMRA model and showed that the risk for all miners was significantly lower (p < 0.0001) with the ventilation system on than when the system was off. Our study showed that the use of a ventilation system at the adit level of the mine reduced the risk of infection with aerosolized L. pneumophila.
    • Quantifying pathogen infection risks from household laundry practices

      Reynolds, Kelly A.; Verhougstraete, Marc P.; Mena, Kristina D.; Sattar, Syed A.; Scott, Elizabeth A.; Gerba, Charles P.; The Mel and Enid Zuckerman College of Public Health, University of Arizona; Department of Environmental Sciences, University of Arizona (Wiley, 2021-09-18)
      Aims: Contaminated laundry can spread infections. However, current directives for safe laundering are limited to healthcare settings and not reflective of domestic conditions. We aimed to use quantitative microbial risk assessment to evaluate household laundering practices (e.g., detergent selection, washing and drying temperatures, and sanitizer use) relative to log10 reductions in pathogens and infection risks during the clothes sorting, washer/dryer loading, folding and storing steps. Methods and Results: Using published data, we characterized laundry infection risks for respiratory and enteric pathogens relative to a single user contact scenario and a 1.0 × 10−6 acceptable risk threshold. For respiratory pathogens, risks following cold water wash temperatures (e.g. median 14.4℃) and standard detergents ranged from 2.2 × 10−5 to 2.2 × 10−7. Use of advanced, enzymatic detergents reduced risks to 8.6 × 10−8 and 2.2 × 10−11 respectively. For enteric pathogens, however, hot water, advanced detergents, sanitizing agents and drying are needed to reach risk targets. Significance and Impact of the Study: Conclusions provide guidance for household laundry practices to achieve targeted risk reductions, given a single user contact scenario. A key finding was that hand hygiene implemented at critical control points in the laundering process was the most significant driver of infection prevention, additionally reducing infection risks by up to 6 log10.