Can humidifier disinfectants increase your risk of lung cancer?

What's actually in it

Humidifier disinfectants are liquid chemicals added to humidifier water tanks to kill bacteria and mold. Common active ingredients include polyhexamethylene guanidine (PHMG), oligo(2-(2-ethoxy)ethoxyethyl) guanidinium chloride (PGH), and chloromethylisothiazolinone (CMIT). When the humidifier runs, these chemicals become aerosolized and you breathe them deep into your lungs.

Unlike chemicals that enter through food or skin, inhaled disinfectants reach the delicate alveoli of your lungs, where there's almost no barrier between the chemical and your bloodstream.

What the research says

A 2025 study in Cancer Epidemiol used propensity score matching to compare lung cancer rates between people who used humidifier disinfectants and those who didn't. This statistical method helps isolate the effect of the disinfectant by matching users and non-users who are otherwise similar in age, smoking history, and health.

People who used humidifier disinfectants had a higher rate of developing lung cancer compared to matched non-users. The association remained after adjusting for smoking status, which is the strongest known risk factor for lung cancer.

South Korea experienced a public health disaster linked to these products, with thousands of cases of lung injury reported. This study extends those findings by showing the connection to cancer specifically, not just acute lung damage.

Don't add any disinfectant chemicals to your humidifier. Clean the tank regularly with white vinegar and water instead. Use distilled water to minimize mineral buildup and bacterial growth. If mold is a recurring problem, the humidifier may need to be replaced.