Methylsiloxanes Found in Air at 1000x PFAS Levels
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- Methylsiloxanes are widely present in the atmosphere across urban, coastal, rural, and forest environments, with concentrations much higher than expected, according to a study led by Utrecht University and the University of Groningen.
- Large molecular methylsiloxanes make up 2% to 4.3% of organic aerosol mass in the atmosphere—orders of magnitude higher than typical atmospheric PFAS levels—and are among the most concentrated synthetic compounds detected.
- Traffic emissions account for over half of the detected large molecular methylsiloxanes, with evidence pointing to lubricant-related sources such as engine oil due to their dispersion pattern matching long-chain hydrocarbons.
- Rupert Holzinger of Utrecht University notes that daily inhalation of methylsiloxanes may exceed that of other synthetic pollutants like PFAS and microplastics, underscoring an urgent need to evaluate health risks.
- Atmospheric samples from the Netherlands, Lithuania, and Brazil show the highest concentrations in São Paulo (98 ng/m³) and the lowest in Lithuanian forests (0.9 ng/m³), indicating broad geographical presence across diverse climates and economies.
- Large molecular methylsiloxanes are chemically stable and resist atmospheric dilution, enabling long-distance transport unlike similar compounds that degrade, increasing their potential for global dispersion.
- Methylsiloxanes may influence cloud formation and climate by altering aerosol surface tension and interfering with ice nucleation, suggesting underappreciated environmental and climatic effects.
Why it matters: Humans are likely inhaling far more methylsiloxanes than other well-known synthetic pollutants, yet health and climate impacts remain unregulated and understudied. With concentrations in urban air exceeding 90 nanograms per cubic meter and evidence of global transport, these findings demand immediate toxicological review and could reshape how regulators prioritize airborne contaminants.
