DNA tech could reveal water contamination

Scientists are developing a new high-tech way to respond to water contamination with DNA-based tracers. Photo / File

Water supply contaminations like that which recently left thousands of people sick in Havelock North could be quickly traced with new DNA-based technology being developed by ESR scientists.

In the weeks following the bacteria contamination of the Hawke's Bay town's water supply in August, which caused about 5200 people to become ill, pin-pointing the exact source proved a headache for investigators.

Current contamination tracking uses fluorescent dye tracers and bromide that are mostly limited to one location at a time, and can be toxic to aquatic organisms if applied at high concentrations.

Other methods such as water quality and isotope analysis, or microbial source tracking, can indicate causes of contamination, but can not identify contamination source locations or pathways.

But cutting edge new DNA tracers, once established and validated, would allow scientists to quickly and accurately track multiple water contaminant sources through all types of freshwater for the first time in New Zealand.

ESR science leader Dr Liping Pang, who is leading a $900,000 project to develop them, said the tracers will be unique, environmentally safe, versatile and relatively inexpensive.

Since synthetic DNA tracers were not derived from the genome of any organism, they did not have any genetic functionality and had no "background" in the environment, yet could be detected with extreme sensitivity using the polymerase chain reaction (PCR).

Using multiple DNA tracers, each with a unique identifier, allowed concurrent tracking of multiple water contamination source locations and pathways, she said.

Her team's proposed solution, microencapsulation, was commonly used in drug delivery, but also novel for tracking water contamination.

The researchers would develop two classes of new double-stranded DNA tracers for pollution tracking.

One type would be used in wastewater and surface waters, which would be better protected from environmental factors such as temperature, chemicals and UV radiation.

The other, "naked" DNA tracers designed for subsurface water, would be transported better into the porous media of aquifers and soils due to their smaller size.

Pang said in a case like the Havelock North outbreak, multiple tracers would be applied to various suspected contamination locations and traced to the end point.

"Based on our preliminary field study, the quantity required for a DNA tracer is one million times less than that needed for a dye tracer."

As individual DNA tracers had their unique identifiers, their concurrent application would allow the identification of multiple water contamination source locations and pathways, she said.

Water samples would be collected downstream and analysed for presence or absence of the applied DNA tracers, in an approach allowing scientists to cover large numbers of water samples in less than three hours.

Pang expected the main users of the tracers would be councils and their contractors, along with government agencies, engineers, farmers, consultants, iwi and companies.

But the underlying technology had potentially much broader applications in tracking materials in other areas, including food security, protection of high-value goods, forensic analysis, medicine and ecology.

The project is supported by the Ministry of Business, Innovation and Employment, and involves collaboration with the University of Canterbury, the University of Calgary, Environment Canterbury, the Canterbury Waterway Rehabilitation Experiment group and Waikato Regional Council.