Ubiquitous Methylsiloxane Pollutant Detected Everywhere, Health Risks Remain Unknown

A baffling chemical pollutant has been detected almost everywhere, leaving scientists with a stark warning: they have no idea what it does to human health.

Methylsiloxane, a specific type of silicone integral to industries, transportation, cosmetics, and household goods, was previously thought to exist only in air near traffic due to industrial evaporation. New evidence shatters that assumption.

A comprehensive analysis led by researchers at Utrecht University reveals that methylsiloxane is present in high concentrations across urban centers, coastal zones, rural landscapes, and deep forests alike. This ubiquity is alarming because the potential health impacts of these airborne pollutants remain entirely unknown.

Dr. Rupert Holzinger, an associate professor at Utrecht University who co-supervised the research, emphasized the severity of the situation. "We estimate that the daily inhalation dose of methylsiloxanes may exceed that of other synthetic compounds, such as PFAS and micro- and nanoplastics," he stated. "We therefore underscore the urgent need for the evaluation of these health impacts."

While synthetic pollutants like PFAS and microplastics are already recognized as pervasive environmental hazards, methylsiloxane has largely been overlooked until now. Previous research indicated that ships and vehicles emit large molecules of this substance that do not evaporate quickly. The Utrecht team sought to determine the true scale of their presence.

To gather this critical data, the team collected air samples from diverse regions across the Netherlands, Lithuania, and Brazil. The results confirm that these large molecular methylsiloxanes are now ubiquitous in the atmosphere, with concentrations far higher than anticipated.

"The findings also suggest that concentrations of methylsiloxane in the atmosphere are much higher than expected," Dr. Holzinger noted.

The disparity in exposure is significant. Concentrations peaked in urban environments, reaching 98 nanograms per cubic meter in samples taken from the sprawling metropolitan area of São Paulo, Brazil. In stark contrast, forest sites recorded the lowest levels, with a reading of just 0.9 nanograms per cubic meter in Rugsteliskis, Lithuania.

Traffic emissions are the primary culprit, accounting for over half of the detected particles, with engine oil identified as the likely specific source. Because methylsiloxanes are found nearly everywhere, humans are almost certainly continuously exposed to them, inhaling considerable amounts without knowing the consequences.

Beyond the immediate health mystery, the researchers warn that these large molecular compounds may also influence climate change. Published in *Atmospheric Chemistry and Physics*, the study concludes that the collective evidence demands immediate action.

"Collectively, these considerations highlight the need for comprehensive and timely research on methylsiloxanes in atmospheric particulate matter, given their potential implications for human health, climate change, and environmental sustainability," the researchers wrote.