From November of 2001 to January of 2002 a contaminated cistern that had collected rain water for the village of Santa Isabel do Ivaí Paraná, Brazil infected more than 600 people with a parasitic disease (Toxoplasma gondii) that can cause, among other symptoms, blindness and mental disorders in infants and people with weakened immune systems.
Getting to the bottom of how this happened – and how similar outbreaks could be prevented – is a process that government management agencies and academic experts are still learning from, more than a decade later.
The 2001-02 T.gondii outbreak in Brazil, which was likely caused by cracks in the villages’ reservoir that allowed runoff to carry cat feces –a vector for the disease- into the water source, was one of five case studies examined as part of an international training program in water risk assessment held in Sao Paolo in July.
Drs. Charles Haas and
Patrick Gurian, from the Department of
Civil, Architectural and Environmental Engineering, were part of a Drexel contingent that traveled to Brazil for 10 days to help teach the workshop. They were joined by representatives from Mexico, Venezuela, Columbia, as well as the host country.
Haas, whose expertise has allowed him to
provide guidance in water contamination scenarios like this on many occasions, brought an important perspective from his years of experience to the workshop. But according to Haas, it was the diversity of the participants’ experiences that added even more value to the event.
“We broke the workshop into groups and looked at case studies from the United States, Brazil, Mexico, Venezuela and various areas of South America and used the latest risk assessment software tools to show how to approach each incident,” Haas said. “Because of the diversity of the participants’ backgrounds and the scenarios we were looking at, there was much to be learned simply through the process of interacting and approaching the cases from different angles.”
One such case had participants analyze microbial contamination risk associated with waste water reuse for agriculture in the United States, Brazil and Mexico.
Using advanced computer algorithms, the groups considered a laundry list of factors –among them, the nature of the watershed, water treatment, distance of travel from water source to the point of treatment and prevalence of irrigating crops with reclaimed water.
A side-by-side comparison of this scenario through the lens of risk assessment experts from three different countries exposed participants up to a variety of new considerations.
“An example of the difference we’re dealing with is that reusing the residuals from wastewater treatment in some areas of Latin America would require much more treatment than is required by U.S. regulations to get the risk level low enough to even be ‘on the charts’ so-to-speak,” Gurian said.
Differences existed, as the groups learned, in every aspect of the assessment process, right down to assumptions about vegetable rinsing at home – tap water in the United States, dilute chlorine in Brazil and Microdyn in Mexico.
There were even variations in the example data available to the teams -in Mexico, the calculations were based on data from raw wastewater irrigation practices due to limited data on reclaimed water.
“One of the things that really opened some eyes, was that higher endemic rates of disease result in much greater levels of microbial contamination in some of these cases,” said Gurian, who took a moment to dip a toe into the water at Sao Vicente’s beach –water that had been associated with several disease outbreaks in the past, though the water quality was good during the group’s field trip.
In the end, the groups produced three risk outputs per country related to E.coli and Norovirus. But a similar message pervaded all the recommendations: susceptible populations -farmers and their families, consumers of fresh vegetables, children and the elderly- should be cautious when consuming leafy greens irrigated by wastewater.
The Quantitative Microbial Risk Assessment Innovation Institute project in Brazil, the CAEE Department’s educational outreach efforts in Canada, the Netherlands and Singapore and Drexel’s CAEE/School of Public Health
partnership with The Indian Institute of Technology, all share a common goal of drawing on the diverse knowledge of risk assessment and public health experts from around the world. Their work to create a
dynamic data base of case studies and information will eventually help direct the response to scenarios like the one that played out in Brazil in 2001-02, and others that happen daily around the world
.
Pictured above left: Cisterns, like this are often used in Brazil to collect rain water in vilages. Contamination of a village’s water source led to the Brazilian T.gondii outbreak in 2001. Above right: One case study at the workshop, asked participants to compare water reuse for irrigation in Brazil, Mexico and the United States.