While concerns about air pollution for vehicles, power stations etc make headline news, the quality of the air in our houses is overlooked, according to researchers at the 2019 AAAS meeting held in Washington DC 14-17 February.
Cooking, cleaning and other routine household tasks generate significant quantities of volatile and particulate chemicals inside the average home, leading to indoor air quality levels on a par with a polluted major city, said a researcher from Colorado University Boulder. Not only that but these chemicals, from products such as shampoo, perfume and cleaning solutions also find their way into the external environment, making up an even greater source of global atmospheric pollution than vehicles.
‘Homes have never been considered an important source of outdoor pollution and the moment is right to start exploring that,’ said Marina Vance, assistant professor of mechanical engineering at CU Boulder. ‘We wanted to know how do basic activities such as cooking and cleaning change the chemistry of a house?’
In 2018, Vance co-led the collaborative HOMEChem field campaign, which used advanced sensors and cameras to monitor the indoor air quality of a 112m2 manufactured home on the University of Texas Austin campus. Over one month, Vance and her collaborators from a number of other US universities conducted a variety of activities, including cooking toast to a full thanksgiving dinner in the middle of the summer for 12 guests, as well as cleaning and similar tasks.
Although the results of the project have yet to be published, Vance noted that the experiment had shown that homes need to be well ventilated while cooking and cleaning, because even boiling water on a gas hob can contribute to high levels of gaseous pollutants and suspended particulates, with negative health impacts. ‘Even the simple act of making toast raised particle levels far higher than expected, ‘ said Vance. ‘We had to adjust many of the instruments.’
The increasing importance of household chemical pollutants was emphasised by Joost de Gouw, a CIRES visiting professor at CU Boulder. In 2018, his research team published results showing that regulations covering automobiles had pushed transportation-derived emissions down in recent decades while the relative importance of household chemical pollutants had only gone up (Science, doi: 10.1126/science.aaq0524).
Further, children living in homes with all vinyl flooring or flame-retardant chemicals in a sofa have significantly higher concentrations of potentially harmful semi-volatile organic compounds (SVOCs), according to research revealed by a team from Duke University, US.
The researchers discovered that children living in homes where the sofa in the main living area contained polybrominated diphenyl ethers (PBDEs) in the foam had a six-folder higher concentration of PBDEs in their blood serum. Children from homes that had vinyl flooring throughout were found to have concentrations of benzyl butyl phthalate metabolite in their urine that were 15 times higher than children living in homes without vinyl flooring.
‘SVOCs are widely used in electronics, furniture and building material and can be detected in nearly all indoor environments,’ said Heather Stapleton, an environmental chemist at Duke’s Nicholas School of the Environment, who led the study. ‘Human exposure to them is widespread, particularly for young children who spend most of their time indoors and have greater exposure to chemicals found in household dust.
‘We quantified 44 biomarkers of exposure to phthalates, organophosphate esters, brominated flame retardants, parabens, phenols, antibacterial agents and perfluoroalkyl and polyfluoroalkyl substances (PFAS),’ she added.
‘Ozone and fine particles are monitored by the EPA, but data for airborne toxins like formaldehyde and benzene, and compounds like alcohols and ketones that originate from the home are very sparse,’ said de Gouw. While he believes that is too early on in the research to make recommendations on policy or consumer behaviour, he says it is encouraging that the scientific community is now thinking about the so-called esosphere, derived from the Greek word eso, or inner. ‘We need to refocus research efforts on these sources and give them the same attention we have given to fossil fuels. The picture that we have in our heads about the atmosphere should now include a house.’