Second-hand smoke exposure during childhood leaves its mark on children's DNA
A new study shows that postnatal exposure to tobacco smoke alters DNA methylation, which may help explain adverse health effects
Barcelona Institute for Global Health (ISGlobal)
Children exposed to second-hand smoke at home are more likely to show certain changes in the epigenome, which can alter the way genes are expressed. These epigenetic changes could influence the development of diseases in the future. This is the main conclusion of a study led by the Barcelona Institute for Global Health (ISGlobal), a centre supported by the "la Caixa" Foundation. The results, published in Environment International, highlight the need to reduce exposure to second-hand smoke, especially in children's environments.
Our DNA acts as an instruction manual for the body. Without changing the contents of the "book" (i.e. the gene sequence), tobacco smoke can add "marks" to certain pages, affecting the way these instructions are read. One of these marks, DNA methylation, is one of the main epigenetic mechanisms, allowing gene expression to be turned on or off.
Second-hand smoke’s mark on the DNA
While the effects of maternal smoking during pregnancy have long been known to affect the epigenome, this research is among the first to show how second-hand smoke exposure during childhood may also have an effect.
The study included data from 2,695 children from eight European countries: Spain, France, Greece, Lithuania, Norway, the Netherlands, the UK and Sweden. The participants were aged 7-10 years and were volunteers from six cohorts of the Pregnancy and Childhood Epigenetics Consortium (PACE).
Using blood samples from participants, the team looked at the level of methylation at specific DNA sites along the genome and related it to the number of smokers in the household (0, 1, or 2 or more).
DNA methylation changes were identified in 11 regions (called CpGs) that were associated with exposure to second-hand smoke. Most of these regions had also been linked in previous studies to direct exposure to tobacco in active smokers or during pregnancy. In addition, six of them are associated with diseases for which smoking is a risk factor, such as asthma or cancer.
"Our study shows that second-hand smoke during childhood leaves its mark at the molecular level and can alter the expression of genes that influence disease susceptibility in adulthood", says Marta Cosin-Tomàs, ISGlobal researcher and first author of the study.
A global problem with long-term consequences
Despite increasing regulation of smoking in public places, the household remains a major source of second-hand smoke exposure for children. In 2004, it was estimated that 40% of children worldwide were exposed to tobacco smoke. Childhood exposure to this pollutant not only increases the risk of respiratory and cardiovascular disease, but can also affect neurological development and immune function.
"The results suggest that second-hand smoke in childhood leads to epigenetic changes similar to those observed with intrauterine exposure to tobacco or active smoking. This underlines the urgency of implementing comprehensive measures to reduce childhood exposure to tobacco smoke, both at home and indoors", says Mariona Bustamante, ISGlobal researcher and senior author of the study.
"It is not a question of appealing to the individual responsibility of families: exposure to tobacco is a public health problem and hides an issue of social inequality. Socio-economic and environmental factors, together with the influence of powerful commercial interests, make it difficult to reduce exposure to second-hand smoke in certain households," concludes Marta Cosin-Tomàs.
Reference
Cosin-Tomas, M., Hoang, T., Qi, C., Monasso, G. S., Langdon, R., Kebede Merid, S., Calas, L., de Prado-Bert, P., Richmond, R., Jaddoe, V. V., Duijts, L., Wright, J., Annesi-Maesano, I., Grazuleviciene, R., Karachaliou, M., Koppelman, G. H., Melén, E., Gruzieva, O., Vrijheid, M., ... Bustamante, M. (2025). Association of exposure to second-hand smoke during childhood with blood DNA methylation. Environment International, 195, 109204. https://doi.org/10.1016/j.envint.2024.109204
Journal
Environment International
Method of Research
Observational study
Subject of Research
People
Anti-smoking program adds wastewater-based epidemiology to track nicotine use in communities
Research sleuths at University of California, Merced applying sewage-testing tools that were put to powerful use at height of COVID
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Research led by University of California environmental engineering Professor Colleen Naughton will use wastewaster-based epidemiology to measure nicotine use in local communities.
view moreCredit: University of University, Merced illustration
University of California, Merced's Nicotine and Cannabis Policy Center has embarked on an innovative partnership with researchers at the university who track an entire community’s health and habits with samples of human sewage.
The project aims to determine trends and levels of nicotine use in San Joaquin Valley communities through chemicals in wastewater. Collecting hard data on smoking and vaping can aid NCPC’s mission to help local public health agencies, community organizations and tobacco-control researchers give informed responses to the problem.
Traditional methods of collecting data about nicotine use, such as surveys and phone calls, often suffer from low response rates and difficulties in connecting with hard-to-reach populations.
Tobacco is a significant health concern in the Valley’s rural areas. The prevalence of cigarette smoking among rural adults in the United States was reported at 28.9%, notably higher than the general adult population's 11.5% in 2021. Smokeless tobacco also is used more extensively in rural areas than in urban communities.
The persistent popularity of vaping, especially among younger users, makes it all the more challenging to educate people about nicotine’s health dangers and to influence effective policies against the availability and sales and nicotine products.
NCPC, part of UC Merced’s Health Sciences Research Institute, was created in 2018. In 2024, it earned a $3.9 million grant from the University of California’s Tobacco-Related Disease Research Program, extending NCPC’s work for at least four years.
The UC tobacco research program also is the source of three $50,000 grants the NCPC can award for pilot research projects. The first went to the wastewater-detection project, led by UC Merced environmental engineer Professor Colleen Naughton.
Naughton is working with UC Merced environmental engineering Professor Marc Beutel and San Diego State University public health Professor Eunha Hoh. The project will start by collecting wastewater from two cities in Merced and Stanislaus counties and from the UC Merced campus. Sewage samples will be analyzed for nicotine metabolites over a span of several months, allowing researchers to observe trends and patterns of use.
“You can see if it’s increasing or decreasing at certain times of the year. You also can see if your interventions are working, based on whether concentrations rise or fall,” said Naughton, who expects to have the pilot project running by this summer.
Public health Professor Arturo Durazo, NCPC’s director, said detecting nicotine levels in wastewater can establish a new model for tracking actual substance use.
“We continue to have significant gaps in reliable measurements of how many people smoke or use other tobacco products in the San Joaquin Valley. This could help fill those gaps,” Durazo said. “From there, perhaps the research could extend to other substances such as cannabis, alcohol or fentanyl.”
Naughton and her FEWS-US lab gained wide attention during the COVID-19 pandemic when they developed the first global dashboard for wastewater monitoring of SARS-CoV-2, the COVID virus. Wastewater-based epidemiology expanded around the globe during the pandemic. The Naughton lab’s @COVIDPoops19 account on X, formerly known as Twitter, shared findings from multiple continents.
Today, Naughton co-leads Healthy Central Valley Together, which monitors wastewater in Merced, Stanislaus and Yolo counties to track diseases and infections such as influenza, hepatitis, candida and respiratory syncytial virus, or RSV.
Durazo said the remaining two $50,000 grants will be awarded once a year for early career investigators who want to do pilot research that can help shape tobacco and nicotine policies. The work by Naughton and her successors can lay the groundwork for more extensive, federally funded research.
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