HMN 2026: How Early-life indoor mold is linked to reduced childhood lung function, long-term

Mold is a silent threat, often going unnoticed as it quietly harms health. What’s concerning is that exposure to mold during early childhood leaves its mark way into adolescence. In a study published in Environmental Research: Health, a team from the University of Bristol, UK, tapped into data from the Avon Longitudinal Study of Parents and Children (ALSPAC)—a well-known birth cohort study also known as Children of the 90s—to explore how early-life exposure to indoor mold may affect lung function, its development over time, and the risk of doctor-diagnosed asthma.

The researchers analyzed medical data from nearly 14,000 children, whose health and development were followed closely from birth through to approximately 24 years of age, using information collected from clinic visits and questionnaires.

The data indicated that serious exposure to indoor mold at age 5 was associated with a nearly 6% reduction in lung function by age 15. There was also a strong association with asthma, with children exposed to serious mold by age 5 being 1.85 times more likely to have been diagnosed with asthma by age 8 compared to those with no mold exposure. This link, however, weakened as the child approached adulthood.

The growing mold problem

Mold is everywhere, both indoors and outdoors. It can enter the home through doors, windows, vents, and HVAC systems or hitch a ride on clothes, shoes, or pets from outside. Once the mold spores find their way onto damp surfaces, they rapidly grow and spread.

Exposure to indoor mold is surprisingly common. A 2019 report by the UK Center for Moisture in Buildings suggests that up to one-third of UK homes may be affected, while a 2012 European meta-analysis estimated that around 15% of households experience mold.

This problem is likely to grow as climate change brings more floods, storms, and humid conditions—perfect environments for mold to thrive. With most people spending most of their day indoors, increasing exposure to indoor mold is a serious public health concern.

Although indoor mold has been associated with asthma and respiratory symptoms, its effect on objective measures of lung function—particularly in younger populations—remained rather unclear.

The researchers looked at two key ways to measure lung capacity. The first, FEV1, or Forced Expiratory Volume in one second, shows how much air a person can blow out in just the first second of a strong exhale. The second, FVC, or Forced Vital Capacity, measures the total amount of air a person can push out after taking their deepest breath.

The data were from the ALSPAC study, which included pregnant women residing in the Avon area of the UK with expected delivery dates between April 1, 1991, and December 31, 1992, along with their offspring—the children born to those pregnancies.

At ages 8, 15, and 24, participants visited clinics for spirometry testing, in which they breathed into a device that measured FEV1 and FVC to evaluate their lung health. At the same time, they were asked whether a doctor had ever diagnosed them with asthma, allowing researchers to track the condition alongside lung function over time.

The results revealed that early-life indoor mold exposure led to reduced lung function at ages 8 and 15 (5.7% drop in FEV1 and a 6.0% drop in FVC), but not at 24. Exposure was also strongly associated with having an asthma diagnosis at age 8, but the trend weakened by age 24.

Researchers believe that more work is needed to determine whether childhood is a vulnerable window for mold-related lung problems or whether the effects are driven primarily by the timing of exposure.

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