Nonstick chemicals and pregnancy
One of the main types of water-repellent chemicals used today is a fluorine-containing series known as the perfluorinated compounds, which also exhibit resistance to stains and grease. They are used worldwide in a broad range of consumer products such as cookware, food packaging, clothing, soft furnishings and home cleaning products.
While they fulfil important functions in the home and workplace, they bring with them serious environmental and health concerns, as is the case for many industrial chemicals. The PFCs accumulate and persist in the environment and also appear to persist in humans, where they have been associated with reduced birth weight and changing hormone levels in the thyroid gland.
For these reasons, the PFCs perfluorooctane sulfonic acid (PFOS), its salts, and perfluorooctane sulfonyl fluoride, were added to the Stockholm Convention on persistent organic pollutants in 2009.
These concerns have also kick started a plethora of research studies in labs around the world as we try to understand exposure to PFCs and their health effects. In Canada, one major study is examining the effects of PFCs and the polybrominated flame retardants on thyroid hormone levels during pregnancy, which are involved in foetal brain development.
Under the banner Chemicals, Health and Pregnancy Study (CHirP), researchers have begun by surveying homes of pregnant women in Vancouver to try and establish the main routes of exposure to PFCs.
Mahiba Shoeib, Tom Harner and Sum Chi Lee from the Atmospheric Science and Technology Directorate, Environment Canada, and Glenys Webster from the University of British Columbia, Vancouver, described their work as the first comprehensive study investigating the exposure of pregnant women to PFCs in Canada, although the results will have implications for other developed countries.
Home work on PFCs
The researchers collected indoor air and dust from the homes of pregnant volunteers. The air was sampled on passive samplers containing sorbent disks and the dust was taken from vacuum cleaners. They also gathered lint from clothes dryers as a surrogate means of assessing PFCs on clothing and subsequent dermal absorption.
The neutral PFCs such as fluorotelomer alcohols (FTOHs), perfluorooctanesulphonamide (FOSA) and perfluorooctane sulphonamidoethanols (FOSEs) were measured by GC/MS with positive-ion chemical ionisation, using isotope-labelled analogues as internal standards for more accurate quantification.
The acidic PFCs, which included perfluoro carboxylic acids and PFOS, were measured by LC-tandem-MS with labelled perfluooctanoic acid as an internal standard.
The dominant PFCs in homes
The dominant PFCs in indoor air were FTOHs which accounted for 92% of the neutral PFCs. Their total concentrations were 890-47,000 pg/m3, with the most abundant individual compound being 8:2-FTOH at a mean of 2900 pg/m3. There were some indications that there was a fresh and common source of several FTOHs within the same home.
Other neutral PFCs found included FOSEs and FOSA, with methyl-FOSE being the dominant compound in this group.
The levels of FTOHs were similar to those from earlier studies in homes in Ottawa and Tromso, Norway, suggesting that they might be present at the same level in industrialised areas generally.
However, the levels of FOSA and FOSEs were much lower than those in Ottawa, possibly reflecting a difference in indoor sources.
The measurements of ionic PFCs in indoor air were the first reported for North America. Here, the dominant acid was PFOA which was found in all samples at a mean of 28 pg/m3. The levels of ionic PFCs were about 50 times lower than those of the neutral PFCs, reflecting their lower volatility.
As for the dust, the neutral PFCs were again dominated by 8:2 FTOH, with a mean value of 88 ng/g. The major acidic compounds were PFOA and PFOS at 1.5-4700 and 2.0-1400 ng/g, respectively.
Total PFC levels in lint were about an order of magnitude lower than those in house dust, which might partly be due to their elimination during heating in the dryer.
Adult and infant PFC exposure
The data gathered here were used to estimate exposure of toddlers and adults to PFCs in the home. Inhalation represented the major pathway for adults for ionic and neutral PFCs at 2.7 and 48 ng/day, respectively. These levels represent about 28% of the estimated daily dietary intake for Canadians.
For young children, the contribution of PFCs in dust is far greater. Exposure to ionic PFCs is 17 ng/g dust compared with 2 ng/g for inhalation. However, for the neutral PFCs inhalation still dominated. The overall exposure of toddlers was estimated to be more than 50 ng/day, which is roughly the same level as for adults.
This study illustrates the importance of the indoor environment when considering exposure to perfluorinated compounds. The researchers acknowledged that more data is required to understand the trends of exposure over time and to consider the effects of replacement PFCs produced as a result of the new additions to the Stockholm Convention.