Researchers at York University have found little evidence that sea spray is a significant source of forever chemicals exposure in coastal environments.
The study examined Newfoundland and Labrador, where strong winds, crashing Atlantic waves and an extensive coastline create ideal conditions for marine aerosols to form and travel inland.
The research challenges earlier studies suggesting that sea spray could be an important route for forever chemicals, also known scientifically as per- and polyfluoroalkyl substances (PFAS), to move from the ocean into the atmosphere and onto land.
While forever chemicals were detected at every location studied, the evidence suggested they had mainly travelled through the atmosphere from distant sources rather than arriving via sea spray.
The researchers also found that dry deposition, where chemicals and particles settle directly from the atmosphere, was an important contributor to PFAS contamination.
The finding could improve understanding of how exposure to forever chemicals occurs in coastal environments far from the industrial and commercial areas where these persistent substances are produced and used.
Investigating forever chemicals in sea spray
The York University team, led by PhD student Daniel Persaud and atmospheric chemist Professor Cora Young, set out to determine whether sea spray was carrying forever chemicals from the Atlantic Ocean into nearby terrestrial environments.
Newfoundland and Labrador provided a particularly strong test case. The region faces powerful winds and frequent wave activity, producing substantial quantities of marine aerosols.
The researchers therefore expected to find a strong connection between sea spray and forever chemicals deposited on land.
The team collected samples from forested watersheds at several sites extending up to 30 kilometres inland from the eastern coast.
The team examined both wet deposition, such as rain, and dry deposition, involving atmospheric particles and gases that settle onto the ground without precipitation.
Researchers used sodium as a marker for marine aerosols because it is a major component of sea salt. A strong relationship between sodium and forever chemicals would have indicated that sea spray was helping transport the substances inland.
Instead, the measured concentrations showed little association with sodium.
Forever chemicals travelled from distant sources
Although forever chemicals were found at all of the study sites, their chemical composition provided clues about their origin.
The researchers mainly detected perfluoroalkyl acids, a group of PFAS that includes perfluoroalkyl carboxylic acids and perfluoroalkanesulfonic acids. These compounds were not linked to local sources in Newfoundland.
The evidence instead points to precursor chemicals being transported through the atmosphere from elsewhere before breaking down into the compounds the researchers detected.
Potential sources include industrial and commercial centres elsewhere in Canada and the United States, although atmospheric transport means the chemicals could have originated much further away.
Forever chemicals are used in a range of industrial and commercial applications, including firefighting foams, non-stick materials and performance chemicals. Their persistence and ability to travel long distances have resulted in their detection in remote environments, including the Arctic.
For coastal communities, the results suggest that forever chemicals exposure caused specifically by ocean-to-land transport through sea spray may be considerably less important than previously believed.
Dry deposition could be an overlooked pathway
A key finding from the study concerned how forever chemicals reach the environment.
Atmospheric research does not always measure dry deposition alongside rainfall and other forms of wet deposition.
By examining both, the York University team found evidence that chemicals settling directly from the atmosphere can make an important contribution, even in a region where rainfall is frequent.
This is significant because forever chemicals can travel long distances before being deposited. Identifying whether they arrive through rain, snow or dry atmospheric deposition can help researchers understand where they accumulate and how contamination spreads.
The finding may also be relevant to remote environments with few obvious local sources of forever chemicals, where atmospheric transport can still introduce them.
Sea spray appears to play a smaller role
The results suggest that sea spray is not a major global source of forever chemicals, even under conditions particularly favourable for marine aerosol formation.
Newfoundland provided what the researchers considered a strong test because it combined high winds, wave activity and extensive coastline.
The absence of a clear connection between sea spray and forever chemicals therefore challenges the idea that ocean-derived aerosols are a major driver of coastal contamination.
Instead, the study points towards long-range atmospheric transport followed by wet and dry deposition as more important pathways.
For understanding exposure to forever chemicals, this distinction matters.
The findings suggest the ocean may not be continually returning large amounts of these persistent substances to coastal land through sea spray, while highlighting the need to investigate less visible forms of atmospheric deposition when assessing where forever chemicals ultimately end up.
