Household hums below hearing range damage mouse kidneys in five-day experiment
Previous studies have hinted that people surrounded by more environmental noise—low, deep rumblings from air-conditioning units, elevator motors, distant traffic and ventilation ducts—tend to have worse kidney function. But these studies could not identify which part of the noise was to blame or the specific ways it might affect the kidneys.
A recent five-day study conducted by researchers at Nagoya University Graduate School of Medicine has revealed that low-frequency noise, typically below the range of human hearing, can cause damage to mouse kidneys. This finding contradicts previous research that suggested environmental noise, regardless of frequency, may negatively impact kidney health.
The team led by Takumi Kagawa and Masashi Kato recorded noise from two household appliances: an air conditioner and a heat pump water heater. They then separated each recording into low-frequency (≤100 Hz) and high-frequency components using audio software. Mice were exposed to these noise types for 12 hours a day, at night, when they are most active.
The results showed that exposure to the low-frequency noise led to elevated levels of creatinine and urea nitrogen in the mice's blood, indicating kidney damage. However, high-frequency noise did not cause any adverse effects. The researchers further investigated the mechanism behind this damage and found that low-frequency noise caused swelling in the kidneys' glomeruli, thickening of their filtering membranes, and increased production of endothelin-1, a molecule that constricts blood vessels.
To confirm this hypothesis, the researchers administered ambrisentan, a drug used to treat hypertension, to a second group of mice. Treatment with ambrisentan reduced renal damage and kidney markers in the treated mice, implying that endothelin-1 signaling plays a crucial role in low-frequency noise-induced kidney injury.
While the study's findings are significant, it is essential to note that mice and humans differ in their ability to perceive low-frequency sounds. Therefore, the relevance of these results to human health remains uncertain. Nevertheless, the study emphasizes the need to consider low-frequency noise in future research on environmental noise exposure and its potential impact on human health.
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