Analytical Science news

Cawthron Technical Officer Geoff Miles
19 August 2019

Measuring methylmercury: Proactive research to protect market access

It’s no secret that fish harvested from New Zealand waters is both delicious and a rich source of nutrition. However, something that’s not yet known is exactly how our fin-fish species measure up for the contaminant methylmercury (MeHg+). That’s about to change, with researchers at Cawthron Institute Analytical Science working to get the facts on methylmercury in New Zealand fish species.

Methylmercury contamination in fish is a well-established issue around the world. Exposure to the contaminant presents a risk to human health, and this is most acute during pregnancy with high levels of gestational exposure impacting fetal brain development. In order to mitigate the risk to vulnerable populations, regulators around the world set guidelines and import standards that balance the many health benefits of eating fish with the risk of consuming MeHg+.

New Zealand Food Safety (NZFS) is actively involved in the development of international regulation that might affect domestic industry through the Codex Alimentarius Commission. Codex has established a large body of international standards and guidance for use by member countries for consumer health protection and trade, and they’re currently considering their settings around methylmercury in fish.

NZFS Food Risk Assessment Acting Manager Dr Andrew Pearson said it’s fantastic to have this domestic research underway. He explained this is a proactive response to growing international interest. “As active participants of Codex, we saw the opportunity for New Zealand to lead with our own survey of key fish species. Regulation setting has traditionally only had access to results for total mercury, but we know from previous research that the toxic methylmercury proportion of total mercury can be as low as 60% in some fish. That’s why it’s important to get the facts around concentrations in our species,” said Dr Pearson.

Fish samples for the survey are being collected through Fisheries New Zealand fishery observers and the ministry has worked with vessel captains to ensure a good geographic distribution. Dr Pearson said he’s pleased with the working relationship between industry and the science providers on this survey phase of the project and believes New Zealand is fortunate to have access to quality research institutes that can help us better understand our species.

“Other countries don’t have anything like the method that Cawthron has developed in terms of consistency. This means consumers can have confidence in the results and ultimately the guidance that will be informed by this research,” said Dr Pearson.

The research project is centred around two certified-sustainable, key New Zealand export species; ling and orange roughy. As methylmercury is known to bio-accumulate in older predator fish, four other species with these characteristics (barracouta, gemfish, smooth oreo, and black oreo) have also been selected for inclusion in the survey.

Developing the methylmercury test method and applying it through the NZ fish species survey has been a natural fit for Cawthron Institute. The organisation provides the seafood sector with world-class science to support sustainable growth and ensure the safety of New Zealand’s marine harvest.

Cawthron Technical Officer Geoff Miles

Cawthron Analytical Science Technical Officer Geoff Miles led the development of the method that is now being used to analyse around 300 fish samples taken from a range of landings. “This research will provide species specific data and the results will be entered into the World Health Organisation GEMS/Food (Global Environment Monitoring System - Food Contamination Monitoring and Assessment Programme) database. This means the information will be widely available to assist importers and exporters.

“The method we’ve developed and are using for this survey has been validated for a range of different fish species and we are pleased to be able to offer this to industry as a commercially-available test. This can be combined with other analysis including nutritional testing for omegas, protein, and iodine.

“Seafood is rich in nutrition, including neuroprotective omega-3 polyunsaturated fatty acids, so it’s important risks are managed without discouraging people from enjoying the health-promoting benefits of eating fish,” said Mr Miles.

As part of this research, lead contract holder ESR (Institute of Environmental Science and Research) is investigating the long chain fatty acids in the surveyed fish species. These results will be paired with the MeHg+ data produced by Cawthron to help decision-makers get the balance right between the various nutritional benefits and the potential health risks.

Seafood New Zealand is supporting this research and for Seafood Standards Manager Cathy Webb it’s a natural next step for the industry. “It’s well known that mercury is a contaminant of concern for overseas markets and our products can be tested for it at international borders. As an industry we’ve been involved in the identification of total mercury in our species for decades,” said Ms Webb, “However, this particular project is important because while many countries focus on total mercury, it’s methylmercury that’s most relevant to consumer health.

“We’ll benefit from better information about the proportion of methylmercury in our fish, rather than relying on total mercury as a screen in lieu of better information. It’s also positive we now have the ability to test for methylmercury here in New Zealand because it means we can respond quickly should regulators need more information.

“We access a wide range of export markets and the NZ Seafood Standards Council works closely with NZFS to have input to international standard setting through the Codex process. This proactive approach means we’re able to advocate for appropriate and consistent standards across markets, making it possible for our industry to supply quality seafood to the world,” said Ms Webb.

With the survey and analysis expected to be complete before the year is out, regulators and scientists will move into 2020 with a better understanding of methylmercury in the New Zealand context. Looking to the future, this proactive research will help ensure ongoing international market access and confidence in New Zealand’s quality seafood sector; meaning people at home and abroad can continue to enjoy the many benefits of New Zealand wild-caught fish.