As PEX (cross-linked polyethylene) piping becomes more popular in residential plumbing due to its flexibility, affordability, and ease of installation, questions have emerged about its potential long-term health impacts — particularly for people with asthma or other respiratory conditions.

While no definitive, large-scale epidemiological studies have directly tied PEX piping to asthma, early research and emerging evidence raise enough concerns to warrant caution and further investigation.

Chemical Leaching from PEX Pipes

PEX pipes are manufactured using various chemicals and stabilizers that can leach into the water — especially when the pipes are new or exposed to high temperatures. Some of the most commonly detected compounds include:

• Tert-butyl alcohol (TBA)

• Methyl tert-butyl ether (MTBE)

• Ethyl tert-butyl ether (ETBE)

These substances are volatile organic compounds (VOCs) and are often used as solvents or fuel additives. While these chemicals typically dissipate over time, they are detectable in water during the first months after installation. According to a 2021 study published in the International Journal of Environmental Research and Public Health, the levels tend to decline after routine flushing and aging of the pipe.

Although there is no direct clinical evidence that these specific VOCs from PEX pipes cause or worsen asthma, VOC exposure in general is a known respiratory irritant. For children, the elderly, and individuals with compromised lung function, even low-level exposure may be problematic.

Microplastics: A Growing Concern

In addition to VOCs, PEX pipes may contribute to the release of microplastics and nanoplastics into household water supplies. Over time, friction, temperature changes, or chemical interactions can cause the plastic material to degrade into microscopic particles.

Why this matters for asthma:

Recent laboratory and animal studies suggest that inhalation or ingestion of microplastics may lead to:

• Chronic lung inflammation

• Oxidative stress and mitochondrial damage in lung cells

• Immune dysregulation

• Worsening of pre-existing respiratory diseases, including asthma

While most studies on microplastic exposure focus on ingestion through food or water, research also indicates that microplastics can become aerosolized, especially in homes where hot water vapor is present (e.g., showers, humidifiers, kettles). If these particles are inhaled, they could contribute to airway inflammation.

More research is needed, but early findings from environmental health and toxicology fields suggest a clear link between plastic degradation and respiratory stress.

Plumbing Failures, Mold, and Indoor Air Quality

It’s not just the material of the pipe that can affect respiratory health. Poor installation, temperature fluctuations, or long-term wear can cause PEX pipes to crack or leak. Even a minor leak inside a wall can foster mold growth, and mold is a well-documented asthma trigger.

In homes with damp conditions or concealed leaks, mold spores can circulate through HVAC systems and indoor air, potentially worsening asthma symptoms or causing new sensitizations.

What Should Homeowners Do?

If you’re concerned about PEX piping in your home — especially if someone in the household has asthma — here are some practical recommendations:

• Flush thoroughly: After new installation or renovations, run hot and cold water to flush out initial chemical residues.

• Water testing: Test for VOCs and microplastics using a certified lab if you’re noticing chemical tastes, odors, or health symptoms.

• Ventilation is key: Ensure bathrooms and kitchens are well-ventilated to reduce vaporized chemical exposure.

• Inspect regularly: Watch for signs of leaks, discoloration, or warping in pipes or walls — and fix issues promptly.

• Monitor symptoms: If you or someone in your home has unexplained asthma flare-ups or skin/eye irritation, consider whether piping materials might be contributing.

Conclusion

While PEX piping is widely used and considered safe by building codes, emerging evidence suggests it may not be entirely inert — especially in the first few months after installation or under certain heat and water conditions. For people with asthma or chemical sensitivities, the presence of VOCs, microplastics, or hidden mold should be taken seriously.

Until more is known, it’s wise to stay informed, maintain your plumbing system, and make decisions based on the needs and vulnerabilities of your household.

Sources:

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7915131/

   (“Volatile Organic Compounds from PEX Plumbing and Human Health” – IJERPH, 2021)

2. https://safepipingmatters.org/2023/12/01/plastic-pipes-microplastics-impacts-on-human-health/

   (“Plastic Pipes, Microplastics, and Impacts on Human Health” – Safe Piping Matters)