According to the study, the report found that 6 out of every 10 people on Earth do not have access to flush toilets or other adequate sanitation - measures that protect the user and the surrounding community from harmful health effects.
Jamie Bartram, Ph.D., and colleagues explain that the current definition of "improved sanitation" focuses on separating humans from human excrement. However, it does not include treating that sewage or other measures to prevent it from contaminating rivers, lakes and oceans.
Using that definition, 2010 United Nations estimates concluded that 4.3 billion people had access to improved sanitation and 2.6 billion did not.
The new estimates used what the authors regarded as a more realistic definition from the standpoint of global health, since untreated sewage is a major cause of disease.
They refined the definition of "improved sanitation" by discounting sewage systems lacking access to sewage treatment.
They concluded that about 60 percent of the world's population does not have access to improved sanitation, up from the previous estimate of 38 percent.
The findings have been published in ACS' journal Environmental Science and Technology.