Invisible Indoor Threats Emerging Household Contaminants and Their Growing Risks to Human Health

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Children, older adults and people who spend most of their time indoors may face elevated health risks from unseen household contaminants. Researchers now warn that modern buildings can trap and transform chemicals in ways that amplify long-term exposure.

Indoor dust, air and everyday products are exposing people to a growing mix of “new contaminants” inside homes, schools and workplaces, according to a new perspective published in the journal New Contaminants. The authors warn that these emerging chemicals may quietly increase the risk of heart disease, cancer and developmental problems while remaining largely unregulated and poorly monitored indoors.

People now spend about 90 % of their time indoors, yet most pollution research and standards still focus on outdoor air. The paper highlights that indoor spaces have complex mixtures of chemicals from building materials, furnishings, cosmetics, cleaning agents and electronics that can linger and transform over time. Because modern buildings are more airtight to save energy, pollutants released indoors can accumulate and lead to long term exposure.​

“In many buildings indoor pollution can be more severe than what we measure outside and that is especially worrying for children and older adults who rarely leave these environments” says corresponding author Wei Du of Kunming University of Science and Technology. “Our daily routines bring us into constant contact with chemical residues in the air, dust and on surfaces even when we cannot see or smell them.”​

What Are “New Contaminants”?

Unlike traditional indoor pollutants such as formaldehyde or carbon monoxide, new contaminants include persistent organic pollutants, endocrine disrupting chemicals, antibiotics and microplastics that have only recently come under scrutiny. These substances can be released from shampoos, sunscreens, plastics, carpets, paints, toys, electronics and specialized materials used in offices or childcare centers. Once indoors they can enter the body through inhalation, ingestion of dust or skin contact and have been detected in blood, urine, breast milk and even human bone marrow.​

The authors emphasize that indoor surfaces and dust act like chemical reactors where contaminants can change into new compounds that may be even more persistent or toxic than the originals. For example, reactions driven by indoor light, ozone and other oxidants can turn flame retardants or fragrance ingredients into derivatives with stronger neurotoxic or endocrine disrupting effects. These processes make it harder to predict health risks using outdoor studies alone and point to the need for indoor specific research.​

The perspective calls for systematic monitoring of new contaminants in different indoor settings including homes, schools, hospitals, offices and recreational facilities to build a comprehensive database for regulators. The authors argue that high resolution measurements, mechanistic studies of chemical transformations and targeted toxicology work are urgently needed to inform next generation indoor air standards. “Protecting human health increasingly means looking inward at the places where we live, learn and work and treating indoor environments as a critical frontier for pollution control” says co corresponding author Bo Pan.​

Journal Reference: Wang J, Zhou X, Fu N, Zhou S, Yang S, et al. 2025. New contaminants in indoor environments: occurrence, transformation, and health risks. New Contaminants 1: e017

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