Nav: Home

Fluorescence method detects mercury contamination in fish

February 20, 2017

Researchers from the University of Burgos (Spain) have developed a fluorescent polymer that lights up in contact with mercury that may be present in fish. High levels of the metal were detected in samples of swordfish and tuna. According to the conclusions of another Spanish study, mercury exposure is linked to reduced foetal and placental growth in pregnant women.

The presence of the toxic metal mercury in the environment comes from natural sources, however, in the last decades industrial waste has caused an increase in concentrations of the metal in some areas of the sea. In the food chain, mercury can be diluted either in organic form as methylmercury (MeHg+) or as an inorganic salt, the cation Hg2+.

Now, researchers from the University of Burgos have created a fluorescent polymer, JG25, which can detect the presence of these two forms of mercury in fish samples. The development is published in the journal Chemical Communications.

"The polymer remains in contact with samples extracted directly from the fish for around 20 minutes. Then, while is being irradiated with ultraviolet light, it emits a bluish light, which varies in intensity proportionally to the quantity of methylmercury and inorganic mercury present in the fish," explains Tomás Torroba, lead author of the paper.

A portable polymer probe, which can be used in situ, was used to apply the technique to 2-gram samples from a range of fish species. The qualitative relationship between the mercury levels in fish and the increased fluorescence was verified using chemical analysis (called ICP-Mass).

The research showed that the larger is the fish the higher are the levels of mercury: between 1.0 and 2.0 parts per million for swordfish, tuna and dogfish, around 0.5 ppm in conger eels and 0.2 ppm in panga. No mercury was found in farmed salmon. These are large fish and at the top of the food chain, but the metal is not present in captivity due to the lack of an industrial or natural source.

The toxicity of fish depends on the amount mercury found in the fish presented in the diet. According to the recommendations of the European Food Safety Authority (EFSA), the tolerable weekly intake of methylmercury should be no more than one serving containing amounts over 1.6 μg/kg (micrograms per kilogram of fish) or 4 μg/kg for inorganic mercury (this amount is close to the one detected in the study).

However, the current trend for this limit is to be lowered. For example, the United States food safety agency, the FDA, goes beyond this and recommends consuming no more than one portion per week of fish containing concentrations over 1 μg/kg, a tendency other countries are likely to follow.

"Contamination of above 0.5 ppm in a food is already thought to be a considerable level," Torroba explains. "Several of the fresh tuna and swordfish samples we analysed exceed and even double this amount. This is why experts recommend that pregnant women reduce their weekly intake of certain types of fish, such as swordfish, due to possible risks to the foetus."

Mercury in pregnant women

In this context, a study led by researchers from the Foundation for the Promotion of Health and Biomedical Research of the Community of Valencia (FISABIO, for its Spanish abbreviation) and the Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP, for its Spanish abbreviation) has shown that there is an association between prenatal mercury exposure and reduced placenta size and foetal growth.

The study, carried out within the Environment and Childhood (INMA, for its Spanish initials) mother-child cohort project, aimed to evaluate this link using data on 1,869 newborns from different regions of Spain (Valencia, Sabadell, Asturias and Guipúzcoa).

One of the largest studies carried out to date in order to determine mercury levels in umbilical cord blood samples and its association with different reproductive effects: measurements of foetal development (weight, height and head circumference at birth), placental weight, duration of pregnancy and risk of premature birth.

The findings, published in the journal Environmental Research, show a relatively high average mercury concentration in umbilical cord blood (8.2 micrograms per litre), with a 24% of samples exceeding the WHO's provisional tolerable weekly intake equivalent.

"A double in the cord blood mercury concentrations (e.g. a change in the concentration from 8 to 16 micrograms per litre) is associated to a 7.7 gram reduction in the weight of the placenta and also shows a pattern of negative association with the newborn's head circumference," explain Mario Murcia and Ferran Ballester, co-authors of the study. "However no relation was found with other parameters, such as duration of pregnancy."

The results of the INMA project suggest that prenatal mercury exposure may, therefore, be affecting the development of the placenta and foetal growth. Although the magnitude of these potential effects is small, reduced placental weight has been linked to the risk of high blood pressure in adulthood. Head circumference, in turn, has been associated with subsequent cognitive development.

Despite preventive and surveillance measures are been considered for foods, due to the positive effects on health that are also linked to consuming fish, the researchers urge for public health efforts in order to reduce human mercury emissions.
-end-
References:

José García-Calvo, Saúl Vallejos, Félix C. García, Josefa Rojo, José M. García, Tomás Torroba. "A smart material for the in situ detection of mercury in fish". Chemical Communications 52, 11915, 2016.

Mario Murcia, Ferran Ballester, Ashley Michel Enning, Carmen Iñiguez, Damaskini Valvi, Mikel Basterrechea, Marisa Rebagliato, Jesús Vioque, Maite Maruri, Adonina Tardon, Isolina Riaño-Galán, Martine Vrijheid, Sabrina Llop. "Prenatal mercury exposure and birth outcomes". Environmental Research 151: 11-20, 2016

FECYT - Spanish Foundation for Science and Technology

Related Public Health Articles:

Public health guidelines aim to lower health risks of cannabis use
Canada's Lower-Risk Cannabis Use Guidelines, released today with the endorsement of key medical and public health organizations, provide 10 science-based recommendations to enable cannabis users to reduce their health risks.
Study clusters health behavior groups to broaden public health interventions
A new study led by a University of Kansas researcher has used national health statistics and identified how to cluster seven health behavior groups based on smoking status, alcohol use, physical activity, physician visits and flu vaccination are associated with mortality.
Public health experts celebrate 30 years of CDC's prevention research solutions for communities with health disparities
It has been 30 years since CDC created the Prevention Research Centers (PRC) Program, currently a network of 26 academic institutions across the US dedicated to moving new discoveries into the communities that need them.
Public health experts support federally mandated smoke-free public housing
In response to a new federal rule mandating smoke-free policies in federally funded public housing authorities, three public health experts applaud the efforts of the US Department of Housing and Urban Development to protect nonsmoking residents from the harmful effects of tobacco exposure.
The Lancet Public Health: UK soft drinks industry levy estimated to have significant health benefits, especially among children
The UK soft drinks industry levy, due to be introduced in April 2018, is estimated to have significant health benefits, especially among children, according to the first study to estimate its health impact, published in The Lancet Public Health.
Social sciences & health innovations: Making health public
The international conference 'Social Sciences & Health Innovations: Making Health Public' is the third event organized as a collaborative endeavor between Maastricht University, the Netherlands, and Tomsk State University, the Russian Federation, with participation from Siberian State Medical University (the Russian Federation).
Columbia Mailman School Awards Public Health Prize to NYC Health Commissioner Dr. Mary T.
Dr. Mary T. Bassett, Commissioner of the New York City Department of Health and Mental Hygiene, was awarded the Frank A.
Poor health literacy a public health issue
America's poor record on health literacy is a public health issue, but one that can be fixed -- not by logging onto the internet but by increased interaction with your fellow human beings, a Michigan State University researcher argues.
Despite health law's bow to prevention, US public health funding is dropping: AJPH study
Although the language of the Affordable Care Act emphasizes disease prevention -- for example, mandating insurance coverage of clinical preventive services such as mammograms -- funding for public health programs to prevent disease have actually been declining in recent years.
'Chemsex' needs to become a public health priority
Chemsex -- sex under the influence of illegal drugs -- needs to become a public health priority, argue experts in The BMJ this week.

Related Public Health Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#529 Do You Really Want to Find Out Who's Your Daddy?
At least some of you by now have probably spit into a tube and mailed it off to find out who your closest relatives are, where you might be from, and what terrible diseases might await you. But what exactly did you find out? And what did you give away? In this live panel at Awesome Con we bring in science writer Tina Saey to talk about all her DNA testing, and bioethicist Debra Mathews, to determine whether Tina should have done it at all. Related links: What FamilyTreeDNA sharing genetic data with police means for you Crime solvers embraced...