Use of quantitative microbial risk assessment for evaluation of the benefits of laundry sanitation

The goal of this study was to evaluate the risk assessment process for quan tifying the contribution of contamination in the home to microbial infectio ns. Whereas risks of enteric pathogens spread through food has been assesse d, the spread of fecal-oral pathogens through surfaces likely at low rates would be difficult to address through epidemiologic studies. An alternative is quantitative risk assessment. The 4-step process of hazard identificati on, dose-response, exposure assessment, and risk characterization can be us ed; however, exposure assessment may follow a complicated pathway consistin g of survival and transference. Microbial hazards in the home have focused primarily on enteric bacteria. Dose-response data are available; however, t he transfer from the hands to the dose is uncertain. Through day care studi es, Shigella has been shown to be transferred in this manner, and a dose-re sponse model is available. By using these data and information on the trans ference of bacteria between clothing and hands, risk estimates were made fo r contaminated laundry. Risks were calculated as high as 10 per million pop ulation to much lower levels associated with lower excretion rates of the b acteria in the feces. Approximately a 90% and 99% reduction in the probabil ity of disease through laundering and use of a sanitizing detergent, respec tively, were suggested by the models. Better data are needed on incidence o f disease in the population, excretion rates over the course of an infectio n, amount of feces spread in the home, distribution of bacteria, survival, and the transfer of the bacteria from surfaces to the hands and to the mout h.