Are grab-n-go veggies your family’s weeknight meal-time saving grace? Recent studies suggest it’s time to rethink if the convenience is worth the toxic price you pay for pre-washed vegetables

You may already be wise to the false allure of prepared foods, faithfully avoiding grocery store products with long ingredient lists, and anything “instant” or in its own microwaveable dish. But if you think pre-washed vegetables and salad mixes are an exception to the prep-it-yourself rule, it’s time to be aware of the latest scientific findings.

A variety of pre-washed vegetables were recently examined by researchers with the Department of Medical Sciences and Public Health at the University of Cagliari in Italy. The typically healthy foods had been washed and prepared by commercial food prep services and placed in stores as ready-to-eat, fresh vegetables. The samples, including carrots, lettuces, mixed salad, parsley, and garlic, were tested for a type of contaminant known as trihalomethanes, or THMs, a toxic byproduct of water sanitation.

Trihalomethanes are a family of chemicals that can appear in public water supplies that includes chloroform, bromodichloromethane, dibromochloromethane, and bromoform. THMs are created from water treatment and are the result of chlorine, a disinfectant, reacting with the various organic and inorganic matter already in the water. These compounds can be absorbed by different types of foods, including pre-washed, fresh vegetables, and passed into the human bloodstream via digestion.

This study sought to determine the concentration of THMs in different types of ready-to-eat (RTE) vegetables after washing with chlorinated water. Levels were then compared to current safety standards set by the European Union (EU) and the United States (US) for levels of THMs in food processing water supplies.

In the 115 samples that were analyzed, results showed an alarmingly high level of THMs had been absorbed by the vegetables. The average value of total THMs was equal to 76.7 ng g−1, equivalent to roughly 77 parts per billion. Current limits set for THMs in the water used for food processing are 80 µg (micrograms) per liter, or roughly 80 ppb in the EU, and 100 ppb in the US. Chloroform was the THM present in the largest concentration in all the RTE vegetables tested.

The legal limit for total THMs is based on what authorities deem as an “acceptable level of exposure” (which can occur via lungs or digestive system) as calculated over a 70-year life span. The THM concentrations observed in this study were high enough to prompt researchers to declare that “the process of washing RTE vegetables should be optimized in order to reduce the risk for consumers” posed by the presence of these chemicals.

Researchers acknowledge that while levels of trihalomethanes are routinely tested for in the public water supply, little is known about the presence of THMs in foods. The process of washing and preparing soil-grown vegetables and turning them into eye-candy for consumers, exposes the produce to high concentrations of chlorinated water. This study shows that foods exposed to chlorinated water supplies should also be tested, as they can be a primary source of our combined exposure to THMs. In a bitter irony, eating more vegetables—what all healthy lifestyles call for—can be a significant source of dangerous chemicals.

Why We Must Be Vigilant About Water Quality

In our modern era, chronic illnesses are on the rise, prompting many health-conscious individuals to try and make better decisions when it comes to diet. Choices such as drinking a liter or more of water daily and consuming at least 6 cups of fruits and vegetables per day, make up the core of a healthy approach to diet. But if the water is not pure and the produce is laden with cancer-causing chemicals, these otherwise smart choices turn into serious risks to human health.

In many countries of the world, public drinking water has become a repository for toxic waste. According to Environmental Working Group (EWG), more than 250 million Americans are drinking water with unsafe levels of various toxic contaminants, including THMs, arsenic, heavy metals, radiation, PFOA (Teflon), and others. In data collected from environmental agencies from all 50 states between 2010 and 2015, 267 known contaminants were found in public drinking water. These contaminants have been linked to brain damage, cancer, infertility, hormonal problems, and reproductive issues including harm to fetuses and young children, among other risks. The nation’s tap water includes 93 known or probable carcinogens that exceed established regulatory health guidelines.

Long-term exposure to THMs have been linked to increased risks for a variety of health risks, including bladder and colorectal cancers, and heart, lung, kidney, liver, and central nervous system damage. While the International Agency for Research on Cancer (IARC) considers THMs as “possibly carcinogenic to humans,” some studies have shown an association between cancer and exposure to THMs through drinking water. There are a wide range of disinfectant byproducts in drinking water, many of which are known to be genotoxic and carcinogenic.

According to the EPA, short-term health effects due to exposure to THMs, such as through drinking water, are rare and unlikely to result in any risk to health. While the EPA’s final report on the carcinogenic risks of drinking chlorinated water was inconclusive. Officials do admit that these risks are “of strong interest” to public health officials in the US, UK, and Canada. Public water systems are not the only water source where THMs are a concern. According to the Groundwater Association’s website, wellowner.org, chlorination byproducts can be found anywhere chlorine is used, including private wells.

Until our collective scientific examination produces an accurate, long-term assessment of currently allowable limits, it’s best to use reasonable precautions against exposure to THMs. Infants, whose immune systems are not fully developed, and pregnant women may be most at risk. Dangers of reproductive problems, including miscarriage, have been associated with THM exposure.

The Solution: Avoid Tap; Use Filtration

Fortunately, we can greatly limit our exposures by taking simple precautions. If possible, install a high-quality, whole-house filtration system that utilizes activated carbon. If you can’t do whole-house filtration, use a RO-filtration system for your kitchen sink. Distilled water is another safer solution, however it’s important to include adequate amounts of mineralized water to meet daily drinking water needs. If you must use tap water for cooking, pre-boil it.

Bathing or showering in contaminated tap water carries risks from inhaling vaporized THMs. To minimize these risks, take short tepid baths instead of long, hot showers. Concentrations of THMs are substantially higher in hot tap water than in cold water. Other sources of exposure include swimming pools and spas which create a perfect breeding ground for THMs, due to increased use of sanitation chemicals plus more organic matter with which to create the necessary chemical reaction. Swimming in chlorinated pools has been linked to impaired respiratory health due to exposure to these disinfectant byproducts.

There are many people who refuse to accept that our government watchdogs are asleep on the job, who will argue that these chemicals are normally controlled to within legal limits. While this may be an accurate presumption, and legal limits may be set to reasonable levels, our ability to test and monitor a person’s total exposure over time is virtually non-existent. Until better controls are in place, consumers drinking from American taps must operate under the premise that no tap water is safe.