About 2.5 billion people worldwide don't have access to sanitary toilets. Latrines are an option for many of those people, but these facilities' overwhelming odors can deter users, who then defecate outdoors instead. To improve this situation, fragrance scientists paired experts' noses and analytical instruments to determine the odor profiles of latrines with the aim of countering the offensive stench. Their report appears in the ACS journal Environmental Science & Technology.

Poor sanitation, including open defecation, is a major public health issue in many low-income regions. If not contained within a functioning sanitation system, fecal matter can run off into nearby rivers and streams, contaminating drinking water. This in turn can cause health conditions such as childhood diarrhea, which can lead to death in places with inadequate care. Encouraging use of latrines could go a long way toward reducing the risk of illness, but these facilities can be smelly. So, Christian Starkenmann and colleagues at the "fragrance and flavor house" Firmenich brought their scent expertise to bear on the problem.

The scientists figured out an accurate way to identify and quantify the odor-causing compounds present in latrines' "headspace," the air enclosed in these structures. In facilities in India, Kenya and South Africa, the compounds their instruments identified as the most concentrated were responsible for the dominant odors, which the scientists verified by smelling. They say understanding these sensory profiles is critical to countering the odor of sanitation systems and making them more welcoming.