Glowing fish illuminates environmental health hazards
A team of researchers from the University of Exeter and University College London found that environmental oestrogens may contaminate organs that until now scientists had not considered vulnerable to their deleterious effects.
Environmental oestrogens derive from a wide range of chemicals found in sources as diverse as industrial products and pharmaceuticals. Known as endocrine disruptors, they can affect hormone levels, and in humans have been associated with lowered sperm count, as well as increased risk of breast and reproductive cancers. In fish species, research has shown that environmental oestrogens can cause males to gender bend.
Scientists worldwide have tried to devise ways to better understand how these chemicals act in the body and more precisely identify their risks to humans and wildlife. However, tracking the ill-effects of chemical exposure is fraught with complication. Among humans, short of exposing a group of people to a toxin and observing the reaction, it can be difficult to link a particular exposure with a particular outcome. As a result, most research tends to draw associations rather than demonstrate cause and effect.
But the UK team engineered a clever solution. The researchers created a transgenic zebrafish, a species routinely used in toxicology as a model for human health. Its transparent skin allows a view into how its organs form in early life. The group developed a highly sensitive fish that when exposed to oestrogens emits a florescent green signal to show which parts of the body are responding. The model provides an unprecedented look at where the chemicals travel in the body, like an anatomical map of harm.
“This is a very exciting development in the international effort to understand the impact of oestrogenic chemicals on the environment and human health,” says Charles Tyler, an environmental biologist at the University of Exeter and one of the study’s lead investigators. “This zebrafish gives us a more comprehensive view than ever before of the potential effects of these hormone-disrupting chemicals on the body.”
The chemicals tested included compounds found in contraceptive pills and hormone replacement therapy, as well as in paints and industrial detergents. The team also examined the pathway of the common plastics component, Bisphenol A, as it moved through the body.
“We found that these chemicals are penetrating more tissue sights than was envisaged previously,” says Dr. Tyler. “They’re not just affecting the reproductive organs, but also brain and skeletal tissue, and eye function.”
The findings contribute to a body of data mounting steadily since the 1990s on the harms posed by endocrine-disrupting chemicals. But despite the accumulated evidence, translating research into policies that better protect human and ecological health is far from straight-forward. Chief among complications is that the definition of risk is highly politicized, and takes into consideration not only public health but also economic and trade interests.
Take Bisphenol A, for example. One of the most studied – and indicted – of common plastics, the compound has been used for decades in bottles and packaging. Research has linked the product to disorders affecting metabolism, fertility and neurological development, as well as certain cancers and heart disease. In 2010, Canada became the first country to impose an outright ban on the compound, and in 2011 the EU and the UK outlawed its use in baby bottles.
While these moves represent steps toward public health protection, extended regulations are unlikely any time soon. Bisphenol A is relatively cheap and widely distributed in industrial manufacturing, two facts that disincentivize the search for more health-friendly alternatives.
Not only is risk a political and economic issue, but its measurement varies considerably between countries. While the EU has in recent years adopted more stringent policies to ensure that new goods cause minimal harm before being released on the market, in the US much risk assessment takes place after a product has been commercially distributed. As a consequence, the burden of demonstrating that a product poses health or ecological harms often lies in the hands of affected or concerned populations.
In the UK, EU and the US, researchers across scientific disciplines are continuing to monitor the impact of environmental oestrogens as they wind up on consumers’ shelves, inside medicines, and leach into waterways and soils. Dr. Tyler suggests this effort would be strengthened by greater dialogue between fields of study. “I don’t think we link enough between animal and human research,” he says.
In a statement on the significance of the study, Marta Soffker, a researcher in environment and evolution at the University of Exeter who was not involved with the work, suggests the findings are highly relevant to public health. “This work is a great screening tool and has potential to help develop our understanding of how humans, too, may be affected by exposure to these pollutants.”Tagged in: Bisphenol A, chemicals, endocrine disruptors, environment, Environmental oestrogens, glowing fish, health, hormones, nature, pollution, sperm count, toxicology, zebrafish
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