Can boiling and adding lemon to tap water make it safer to drink?

Clean drinking water is vital to human life. In the United States, the chemical chlorine has played a major role in removing harmful bacteria, viruses and other pathogens from drinking water since the early 1900s.

However, using chlorine to disinfect drinking water has its downsides.

“Chlorine not only attacks pathogens, it also attacks other constituents present in the water, such as bromide, iodide and natural organic matter,” explained Virender Sharma, PhD, professor and director of the Program on Environmental Sustainability at the Texas A&M University School of Public Health. “When chlorine attacks these other constituents present in the water, the reaction produces potentially toxic disinfection by-products.”

Long-term exposure to these disinfection by-products via daily tap water ingestion has become a great public health concern. However, previous studies have shown that there are ways of decreasing the levels and concentrations of disinfection by-products in drinking water. One such way is by boiling or heating tap water to higher-than-room temperature. Another strategy is to add lemon to tap water.

With these previous studies in mind, Sharma and collaborators prompted the investigation of a new strategy for controlling disinfection by-products in tap water: combining the effects of lemon and boiling. Their findings were recently published in the journal Chemosphere.

The researchers proposed three different approaches to producing lemon water: 1) adding lemon to tap water at room temperature; 2) adding lemon to boiled tap water and cooling to room temperature; and 3) adding lemon to tap water (at room temperature), then boiling and cooling to room temperature. These three types of lemon water were compared in terms of total disinfection by-products and the by-products’ concentration and toxicity levels.

The results indicated that adding lemon alone to room-temperature tap water could not detoxify disinfection by-products. However, combining the two strategies of boiling the tap water and adding lemon was effective in purifying the tap water. Specifically, adding lemon to tap water before boiling performed best in detoxifying the water.

“It was surprising to find that the order in which the lemon is added and the water is boiled affects the levels and concentrations of disinfection by-products,” Sharma said. “Now we know that adding lemon to tap water before boiling is most effective because it prevents the formation of more disinfection by-products at higher-than-room temperature during the entire heating-boiling-cooling process.”

This study suggests a new strategy for producing lemon water with low levels of disinfection by-products, which could be beneficial to human health. Additionally, this study raises awareness to policy makers, government organizations and other relevant stakeholders that long-term human exposure to disinfection by-products via tap water is avoidable.

-by Callie Rainosek