Friday, 3 February 2017

Substance in Crude Oil Harms Fish Hearts, Could Affect Humans

Research from Stanford University’s Hopkins Marine Station has identified a substance in oil that’s to blame for the cardiotoxicity seen in fish exposed to crude oil spills. More than a hazard for marine life exposed to oil, the contaminant this team identified is abundant in air pollution and could pose a global threat to human health.

The pollutant at the center of this finding, phenanthrene, is a type of polycyclic aromatic hydrocarbon (PAH). Due to widespread use of petroleum, PAHs are also found in land-based stormwater runoff, contaminated soil from defunct industrial sites and air pollution. PAHs have been investigated as cancer-causing chemicals for nearly a hundred years but other potential health effects have been given far less attention. The environmental health risks of phenanthrene, in particular, have received secondary consideration to other PAHs more strongly implicated in the development of cancer.

“By carefully isolating heart cells from tunas, Olympians of the sea, and using electrophysiological and confocal microscopy techniques, we recorded ionic currents and found exactly where phenanthrene blocks the heart excitation-contraction coupling pathway, which is the link between the on-off switch, or excitation, and the contraction that powers every heart beat,” said Barbara Block, professor in marine sciences. Block was senior author of the paper, published in the Jan. 31 issue of Nature Scientific Reports.

The experiments described in the paper provide direct evidence of how phenanthrene impacts the heart, showing how it causes both irregular heartbeat (arrhythmia) and weaker contractions of heart cells. Similar results were found in the heart cells of all three species tested: bluefin and yellowfin tunas and mackerel. At the cellular level, these athletic fish with remarkable aerobic poise are similar to higher vertebrates, which include mammals and birds. This suggests that the cardio-toxicants may also act upon the hearts of higher vertebrates, as all of these animals have similar methods of regulating the activation of heart cells.

“The mechanism which alters cardiac function in fish and the protein that phenanthrene targets – the ion channel responsible for potassium movement from the cell – is also present in humans,” said Fabien Brette, a research associate at Stanford University at the time of the study and co-lead author of the current paper. “What we measured on fish cardiac cells can occur on human cardiac cells and this could mean risk of sudden death.”

Urban air pollution, laden with PAHs, has been implicated in cardiac distress. The current study points the finger at phenanthrene, which could enter the bloodstream through respiratory pathways such as breathing.

[Posted at the SpookyWeather blog, February 3rd, 2017.]

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