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Risk-Based Critical Concentrations of Legionella pneumophila for Indoor Residential Water Uses
Journal article   Open access   Peer reviewed

Risk-Based Critical Concentrations of Legionella pneumophila for Indoor Residential Water Uses

Kerry A. Hamilton, Mark T. Hamilton, William Johnson, Patrick Jjemba, Zia Bukhari, Mark LeChevallier, Charles N. Haas and P. L. Gurian
Environmental science & technology, v 53(8), pp 4528-4541
16 Apr 2019
DOI: https://doi.org/10.1021/acs.est.8b03000
PMID: 30629886
Featured in Collection :   UN Sustainable Development Goals @ Drexel
url
https://doi.org/10.1021/acs.est.8b03000View
Published, Version of Record (VoR)Open Access (Publisher-Specific),  Open

Abstract

Engineering Engineering, Environmental Environmental Sciences Environmental Sciences & Ecology Life Sciences & Biomedicine Science & Technology Technology
Legionella spp. is a key contributor to the United States waterborne disease burden. Despite potentially widespread exposure, human disease is relatively uncommon, except under circumstances where pathogen concentrations are high, host immunity is low, or exposure to small-diameter aerosols occurs. Water quality guidance values for Legionella are available for building managers but are generally not based on technical criteria. To address this gap, a quantitative microbial risk assessment (QMRA) was conducted using target risk values in order to calculate corresponding critical concentrations on a per-fixture and aggregate (multiple fixture exposure) basis. Showers were the driving indoor exposure risk compared to sinks and toilets. Critical concentrations depended on the dose response model (infection vs clinical severity infection, CSI), risk target used (infection risk vs disability adjusted life years [DALY] on a per-exposure or annual basis), and fixture type (conventional vs water efficient or "green"). Median critical concentrations based on exposure to a combination of toilet, faucet, and shower aerosols ranged from similar to 10(-2) to similar to 10(0) CFU per L and similar to 10(1) to similar to 10(3) CFU per L for infection and CSI dose response models, respectively. As infection model results for critical L. pneumophila concentrations were often below a feasible detection limit for culture-based assays, the use of CSI model results for nonhealthcare water systems with a 10(-6) DALY pppy target (the more conservative target) would result in an estimate of 12.3 CFU per L (arithmetic mean of samples across multiple fixtures and/or over time). Single sample critical concentrations with a per-exposure-corrected DALY target at each conventional fixture would be 1.06 x 10(3) CFU per L (faucets), 8.84 x 10(3) CFU per L (toilets), and 14.4 CFU per L (showers). Using a 10(-4) annual infection risk target would give a 1.20 x 10(3) CFU per L mean for multiple fixtures and single sample critical concentrations of 1.02 x 10(5), 8.59 x 10(5), and 1.40 x 10(3) CFU per L for faucets, toilets, and showers, respectively. Annual infection risk-based target estimates are in line with most current guidance documents of less than 1000 CFU per L, while DALY-based guidance suggests lower critical concentrations might be warranted in some cases. Furthermore, approximately <10 CFU per mL L. pneumophila may be appropriate for healthcare or susceptible population settings. This analysis underscores the importance of the choice of risk target as well as sampling program considerations when choosing the most appropriate critical concentration for use in public health guidance.

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3 Record Views
104 citations in Web of Science
101 citations in Scopus

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UN Sustainable Development Goals (SDGs)

This publication has contributed to the advancement of the following goals:

#6 Clean Water and Sanitation
#3 Good Health and Well-Being

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Collaboration types
Domestic collaboration
Web of Science research areas
Engineering, Environmental
Environmental Sciences
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