Methylsiloxanes Detected in Air, Linked to Engine Oil
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- Researchers from Utrecht University and University of Groningen reported widespread atmospheric presence of large molecular methylsiloxanes across urban, coastal, rural, and forest sites.
- Methylsiloxanes constitute 2–4.3 % of the total mass of organic aerosols, making them among the most abundant synthetic compounds in airborne particles—far higher than PFAS, which are >1,000 times lower.
- Engine oil additives containing methylsiloxanes survive combustion and are emitted in exhaust, identified as the primary source of the large‑molecule silicone particles.
- São Paulo recorded the highest concentration at 98 ng m⁻³, while the forest site at Rugsteliskis, Lithuania measured only 0.9 ng m⁻³, illustrating a wide concentration gradient.
- Traffic emissions are responsible for more than half of the detected large‑molecule methylsiloxanes, inferred from dispersion patterns matching long‑chain hydrocarbons from engine oil.
- Inhalation of methylsiloxanes may exceed daily exposure to PFAS and micro‑nanoplastics, and the compounds could alter aerosol surface tension and ice nucleation, potentially affecting cloud formation.
Why it matters: Public health officials and climate modelers must now account for methylsiloxanes, which may exceed PFAS exposure and alter aerosol properties, potentially affecting air‑quality regulations and climate predictions, while industries using silicone additives face scrutiny. Regulators may need to set new emission standards, and researchers will need to study long‑term inhalation effects.
