Quantifying pathogen infection risks from household laundry practices

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.