Increased Risk of Thyroid Cancer From Frequent Use of Disinfectants

Yale researchers have reported that regular exposure to biocides including disinfectants (such as doctors, dentists, nurses, etc) doubles the risk of thyroid cancer. This findings was determined through a population-based case-control study involving 462 thyroid cancer cases in Connecticut collected 2010-2011.

Over the past decade, there has been an increased incidence of thyroid cancer every year and this report may explain part of this alarming trend along with possible over-diagnosis as ultrasound technology and pathology technique has improved. At least in the United States, the average annual increase in the incidence of thyroid cancer is 5%.

Biocide products include not only disinfectants, but also any product capable of deodorizing, sterilizing, sanitizing, and / or killing micro-organisms including bactericides, algicides, fungicides, germicides, and preservatives.

For example, the active ingredient in many "anti-bacterial" soap used in households contains triclosan, a suspected biocide. This biocide is also suspected of causing other types of cancers.

Animal studies have suggested that biocides can trigger thyroid cancer by altering thyroid hormone production. For example, triclosan which is widely found in antibacterial soap is known to decrease serum T3 and T4 thyroid hormones. Drinking water disinfectants including chlorine has also been found to reduce T4 thyroid hormones in animals.

Interestingly, pesticide exposure did not show this same increased risk of thyroid cancer. Pesticides are defined as substances capable of killing some form of organism that is deemed undesirable including insecticides, herbicides, rodenticides, fungicides, molluscicides, and nematodicides.

Obviously, further evaluation is mandated to elucidate the relationship between thyroid cancer and biocide usage. In particular, which exact biocide chemical(s) is/are responsible for this increase given biocides encompass a wide range of chemicals.

Also, there is NO evidence to show that anti-bacterial soap is more effective than regular soap in preventing illnesses. As such, at least for the lay-public, it is recommended to avoid anti-bacterial soap containing any type biocide chemicals and stick with regular soap. Of course for healthcare professionals, we may be out of luck because pretty much any product used to disinfect, clean, sterilize, etc contains biocides. What's worse is that healthcare professionals are exposed to biocides multiple times every day.

Hand-sanitizers should also be avoided, especially if it contains biocides. Triclosan (mentioned above) can quickly absorb through the skin and enter the bloodstream exerting its potentially deleterious effects. If hand-sanitizers are used, ethanol should be the only active ingredient and it MUST be present at concentrations above 60%, otherwise it will be ineffective at killing germs.

References:
Occupational exposure to pesticides and other biocides and risk of thyroid cancer. Occup Environ Med 2017; published online 2/15/17.