The discovery of traces of everyday compounds such as caffeine, artificial sweeteners and pharmaceuticals in groundwater is raising concerns in the science community.
The Institute of Environmental Science and Research (ESR) has been coordinating groundwater surveys since 1990 on behalf of 12 regional and unitary councils. The latest survey was conducted from September to December 2018 and the results released late last year.
For the first time, wells were tested for a range of emerging organic contaminants (EOCs).
ESR principal scientist Murray Close says there is growing concern about EOCs and their potential impact on human and aquatic health, including groundwater.
Mr Close says EOCs are a class of compounds used for everything from the production and preservation of food to personal care products, as well as human and animal healthcare.
The survey tested for close to 30 of these compounds including pharmaceuticals such as pain relief products, contraceptive pills and sunscreen.
“We found these compounds in 70 per cent of wells, and detected 25 of the 29 compounds we tested for,” Mr Close says.
“Ideally, we would do the initial testing for EOCs on a more regular basis, but it takes about two years to do the survey and analyse the results, so it’s not cheap.”
Overseas research links the discovery of EOCs in groundwater to wastewater sources including municipal treatment plants, septic tanks and farming activities, as well as indirectly from surface water.
Mr Close says there are no known health or environmental risks, and there are generally no health guidelines associated with EOCs.
“The contaminants are widely used and do make their way into the environment in low concentrations.
“Most of the time groundwater is out of sight, out of mind. When we do notice it, it’s when something goes wrong, such as the widespread illness linked to a contaminated bore that took place two years ago in Havelock North.”
The survey recommends extending groundwater monitoring and carrying out research to investigate the likely risks for the EOCs detected in the study including any impacts on ecological systems.
The survey also tests for pesticides and glyphosate (the active ingredient in weed killer Roundup).
Glyphosate was found in only one well from the 135 wells tested – and the level detected was well below (over 400 times lower) than the WHO recommended minimum.
“The majority of the wells in the current survey showed no change in the amount of pesticides present compared to previous surveys with less than a quarter of the wells having low levels of pesticides detected.
“None of the sampled wells exceeded safe drinking water standards, with most pesticides detected at less than 0.5 per cent of the maximum acceptable value. A total of 279 wells were sampled and analysed for pesticides, 135 wells were analysed for glyphosate and 121 wells were sampled for ECOs.