"We see signs, for example, of upper-class people now pressuring poor neighbors not to defecate in their fields. It is no longer always a socially acceptable act."
Experts say widespread change won't occur until people understand the connection to public health.
During the monsoon season, when water levels rise, Dr. Singh and his colleagues at the clinic see more than 200 patients a day who suffer from skin boils, intestinal ailments and other maladies attributable to ingesting contaminated water. Almost all have no idea why they are sick.
The doctor says he doesn't expect to see significant change until rural India's notoriously low literacy levels improve.
"They are uneducated and illiterate," Singh says. "When we get a chance, we try to explain the connection between going in the fields and their health. But look at how busy we are. We don't have the time to go into detail with every person."
Yet not everyone sees illiteracy as the root of the problem.
"Even literate people in villages squat outdoors," says Sudhirendar Sharma, a water expert and development analyst with the Ecological Foundation, a nongovernmental agency in New Delhi. "People who have spent all their lives in villages tend to live in a culture in which it is not a taboo to defecate in the open."