Tim Tai

For Yale students, spring break meant catching up on sleep, meeting friends, sightseeing and for some, cleaning out their water bottles.

Lurking in the metal crevices of your Stanley, or snuggled within the silicon lip of your Owala might be a mysterious dark splotch — mold. Should students be concerned about their potential mold exposure?

“Molds can be both beneficial and harmful. Some are useful, while others can pose risks, especially to people with allergies or specific health conditions,” Zheng Wang, a senior research scientist in the Townsend Lab at the School of Medicine, said. “However, except for individuals with severe allergic reactions, most molds in the environment aren’t a major concern.”

Molds are a type of fungi that can be found in a variety of environments, from tropical forests to within our homes.

While mold grows on surfaces rich in organic matter, some species hide on any humid surface, such as the bathtub or kitchen countertops.

Zheng Wang told the News that even though molds are usually not harmful to healthy individuals, some species like yellowish-green Aspergillus produce toxins that can lead to cancer on rare occasions.

“Your mom told you not to eat moldy food because some molds produce and release toxins as they grow – and eating these toxins can make you sick,” Dr. Barbara Kazmierczak, a professor of medicine and microbial pathogenesis, said. “A second risk of drinking mold-containing water is that some of it can go up your nose or into your lungs – and that’s a way of introducing molds into your sinuses or airways.”

Based on a visual analysis alone, it is difficult to ascertain the danger of a mold. 

Denny Wang, a postdoctoral researcher at Yale School of Public Health, studies mycoparasites, fungi that essentially eat other fungi. He says the main concerns with mold are around their secondary metabolites, toxic chemicals they produce to kill competing microbes.

Aflatoxins are one of the most notorious secondary metabolites, which can appear in contaminated peanuts and dried fruit. High doses of these toxins can lead to liver failure, and even low dosage can be carcinogenic, or cancer-causing.

“Fortunately, not all molds are that toxic, and for most people, accidental mold consumption is unlikely to cause severe harm,” Wang said.

Another complication due to exposure to mold is allergies, Wang noted. Coughing and asthma are common symptoms and individual reactions can vary. So, people who are more sensitive should be more cautious about the molds that may exist in their living environment.

According to Wang, rare and sometimes life-threatening fungal infections can occur in immunocompromised patients. These infections can be difficult to treat due to how evolutionarily similar fungi are to humans; antifungals that can effectively kill fungi may harm human cells as well.

As for Yalies who deep-clean their bottles once every break? The concern around mold exposure is minimal.

“If you wouldn’t eat a moldy piece of food or brie, then just wash your water bottle,” Kazmierczak said.

Chaetomium, a common indoor fungus, can cause major health issues.