Nationwide Mass Inventory and Degradation Assessment of Plastic Contact Lenses in US Wastewater

Charles Rolsky, Varun P. Kelkar, Rolf U. Halden

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Plastics pose ecological and human health risks, with disposable contact lenses constituting a potential high-volume pollution source. Using sales data and an online survey of lens users (n = 416) alongside laboratory and field experiments at a conventional sewage treatment plant, we determined the environmental fate and mass inventories of contact lenses in the United States. The survey results revealed that 21 ± 0.8% of lens users flush their used lenses down the drain, a loading equivalent to 44 »000 ± 1700 kg y-1 of lens dry mass discharged into US wastewater. Biological treatment of wastewater did not result in a measurable loss of plastic mass (p = 0.001) and caused only very limited changes in the polymer structure, as determined by μ-Raman spectroscopy. During sewage treatment, the lenses were found to accumulate as fragments in sewage sludge, resulting in an estimated accumulation of 24 »000 ± 940 kg y-1 of microplastics destined for application on US agricultural soils contained in sewage sludge. Recycling of the contact lenses and their packaging amounted to only 0.04% of the total waste volume associated with contact lens use. This is the first study to identify contact lenses and more specifically silicone hydrogels, as a previously overlooked source of plastic and microplastic pollution.

Original languageEnglish (US)
Pages (from-to)12102-12108
Number of pages7
JournalEnvironmental Science and Technology
Volume54
Issue number19
DOIs
StatePublished - Oct 6 2020

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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