Hamilton KA, Ahmed W, Toze S, Haas CN. Human health risks for Legionella and Mycobacterium avium complex (MAC) from potable and non-potable uses of roof-harvested rainwater. Water research. 2017 Apr 5;119:288-303. doi: 10.1016/j.watres.2017.04.004.
A quantitative microbial risk assessment (QMRA) of opportunistic pathogens Legionella pneumophila (LP) and Mycobacterium avium complex (MAC) was undertaken for various uses of roof-harvested rainwater (RHRW) reported in Queensland, Australia to identify appropriate usages and guide risk management practices. Risks from inhalation of aerosols due to showering, swimming in pools topped up with RHRW, use of a garden hose, car washing, and toilet flushing with RHRW were considered for LP while both ingestion (drinking, produce consumption, and accidental ingestion from various activities) and inhalation risks were considered for MAC. The drinking water route of exposure presented the greatest risks due to cervical lymphadenitis and disseminated infection health endpoints for children and immune-compromised populations, respectively. It is therefore not recommended that these populations consume untreated rainwater. LP risks were up to 6 orders of magnitude higher than MAC risks for the inhalation route of exposure for all scenarios. Both inhalation and ingestion QMRA simulations support that while drinking, showering, and garden hosing with RHRW may present the highest risks, car washing and clothes washing could constitute appropriate uses of RHRW for all populations, and toilet flushing and consumption of lettuce irrigation with RHRW would be appropriate for non- immune-compromised populations.
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Martha Sinclair, Felicity Roddick, Thang Nguyen, Joanne O’Toole, Karin Leder. Measuring water ingestion from spray exposures. Water Research 99 (2016)
Characterisation of exposure levels is an essential requirement of health risk assessment; however for water exposures other than drinking, few quantitative exposure data exist. Thus, regulatory agencies must use estimates to formulate policy on treatment requirements for non-potable recycled water. We adapted the use of the swimming pool chemical cyanuric acid as a tracer of recreational water ingestion to permit detection of small water volumes inadvertently ingested from spray exposures. By using solutions of 700-1000 mg/L cyanuric acid in an experimental spray exposure scenario, we were able to quantify inadvertent water ingestion in almost 70% of participants undertaking a 10 min car wash activity using a high pressure spray device. Skin absorption was demonstrated to be negligible under the experimental conditions, and the measured ingestion volumes ranged from 0.06 to 3.79 mL. This method could be applied to a range of non-potable water use activities to generate exposure data for risk assessment processes. The availability of such empirical measurements will provide greater assurance to regulatory agencies and industry that potential health risks from exposure to non-potable water supplies are well understood and adequately managed to protect public health.
Shelly Rodrigo, Martha Sinclair, Andrew Forbes, David Cunliffe, and Karin Leder. Drinking Rainwater: A Double-Blinded, Randomized Controlled Study of Water Treatment Filters and Gastroenteritis Incidence American Journal of Public Health. 2011;101:842-847. doi:10.210B/AJPH.2009.185389)
Objectives. We examined whether drinking untreated rainwater, a practice that is on the rise in developed countries because of water shortages, contributes to community gastroenteritis incidence.
Methods. We conducted a double-blinded, randomized controlled trial in Adelaide, Australia. Sham or active water treatment units were installed, and participants recorded incidences of illness in a health diary for 12 months. The primary outcome was highly credible gastroenteritis (HCG; characterized by a specified number of loose stools or vomiting alone or in combination with abdominal pain or nausea in a 24-hour period), and we used generalized estimating equations to account for correlations between numbers of HCG events for individuals in the same family.
Results. Participants reported 769 episodes during the study (0.77 episodes/ person/year), with an HCG incidence rate ratio (active vs sham) of 1.05 (95% confidence interval [CI] = 0.82, 1.33). Blinding of the participants was effective (index = 0.65; 95% CI =0.58, 0.72).
Conclusions. Our results suggest that consumption of untreated rainwater does not contribute appreciably to community gastroenteritis. However, our findings may not be generalizable to susceptible and immunocompromised persons because these groups were specifically excluded from the study.
Studies such as the one below rely on several assumptions. Addition of fluoride to drinking water is presumed to be necessary to prevent dental caries. Further, advocates and review panels continue to push the idea that an “optimum dose” to drinking water exists. Despite the claims made here the idea that an optimum drinking water dose to a population exists is a default assumption. Time to move on….
Spencer AJ, Do LG. Caution needed in altering the ‘optimum’ fluoride concentration in drinking water. Community Dentistry and Oral Epidemiology. 2015 Dec 29. doi: 10.1111/cdoe.12205.
The US Public Health Service has finalized its recommendation relating to community water fluoridation (Federal Panel on Community Water Fluoridation, US Department of Health and Human Services, 2015). It recommends an optimal concentration of 0.7 mg/l F based on their argument that this concentration provides the best balance of protection from dental caries while limiting the risk of dental fluorosis. The rationale for this recommendation can be questioned, particularly given the contrasting etiologies and impact on the community. Uncertainty surrounds the key evidence considered by the panel. This study argues that the panel should have exercised more caution and called for further research before reducing the ‘optimal’ concentration of fluoride in water supplies. Up-to-date data on caries and fluorosis trend by age group or birth cohort, analyses on attributable risk for fluorosis, data on individual and population impact of caries and fluorosis, water intake over an extended period across the seasons, and the curvilinear relationship of fluoride concentration in water supplies and caries protection would have all been desirable to inform the panel, given the foreshadowing of the recommendation in late 2011. Further, a wider range of policy directions to achieve the best balance of protection from dental caries while limiting the risk of dental fluorosis are available from the international literature. Assessment of these should have been more evident. There is a public health policy responsibility to monitor water fluoridation programs so as to achieve a near maximum reduction in dental caries without unacceptable levels of dental fluorosis. However, recommendations to alter existing policy need to be cognizant of the balancing of risk and protective exposures across the entire population and potentially all ages and to be based on recent data that are purposefully collected, critically analyzed and carefully interpreted.