Studies have shown for some time now that endocrine disrupting substances from chemicals in sewage and other wastewater can affect the normal sex development in fish. Well now, new research indicates that hormone-disrupting pollutants are also affecting the health and development of wild birds nesting along the urban rivers of South Wales.
Researchers studied the Eurasian Dipper, a river bird that feeds exclusively on insects and fish in upland streams, and found that these chicks are underweight compared to their rural counterparts. Also of concern is that birds nesting in urban rivers have altered hormone levels, and are hatching fewer female chicks than those nesting along rural rivers, which could have negative implications for the population’s breeding and survival.
Data obtained by a team of scientists from Cardiff, working in collaboration with the Universities of Saskatchewan and Exeter, and the Natural Environment Research Council, suggest that urban contaminants such as PCBs (polychlorinated biphenyls) and PBDE flame-retardant chemicals (polybrominated diphenyl ethers) acquired through their food are to blame. Results showed a strong correlation between contamination by PBDEs and PCBs with depressed thyroid hormone levels in chicks — one thyroid hormone was 43% lower in chicks from urban rivers than those rural rivers.
Professor Steve Ormerod from the School of Biosciences, who has spent 35 years investigating rivers, commented:
"Our findings are important in showing that pollutants are still a source of concern for the wildlife along Britain’s urban rivers despite very major recovery from the gross pollution problems of the past. Wild birds, such as dippers, are very important indicators of environmental well-being and food-web contamination, and we need to know if populations, other species — or even people - are also at risk."
Dr Christy Morrissey from the School of Environment and Sustainability at the University of Saskatchewan said:
"These are some of the first data to show that PCBs and PBDEs might be causing thyroid disruption in wild birds and interfering with normal animal development."
The effects of thyroid hormone disruptors on birds are diverse but frequently include impaired growth; cognitive dysfunction; compromised immune function changes in motor activity; and behavioral abnormalities that can persist into adulthood.
The study is published in the Environmental Toxicology and Chemistry journal.
Read more at Cardiff University.