Diseases caused by unfiltered or contaminated water are primarily grouped into bacterial, viral, and parasitic infections. Exposure to untreated water can lead to severe gastrointestinal issues, dehydration, and in severe cases, systemic illnesses.
Water and health
Contaminated water and poor sanitation are linked to transmission of diseases such as cholera, diarrhoea, dysentery, hepatitis A, typhoid and polio. Absent, inadequate, or inappropriately managed water and sanitation services expose individuals to preventable health risks.
Polluted or contaminated water is a major vector for diseases, spreading life-threatening bacteria, viruses, parasites, and toxic chemicals. According to the World Health Organization, unsafe water and inadequate sanitation are leading contributors to preventable illnesses globally.
Effects on Human Health
If drinking water contains unsafe levels of contaminants, it can cause health effects, such as gastrointestinal illnesses, nervous system or reproductive effects, and chronic diseases such as cancer.
Yes, unfiltered or untreated water can make you sick. It may harbor harmful bacteria, parasites (like Cryptosporidium and Giardia), and chemical pollutants. This can cause short-term issues like vomiting, stomach cramps, and diarrhea, as well as long-term health problems.
The 10-gulp rule is a hydration habit designed to help you easily meet your daily water intake goals. The rule is simple: Every time your water bottle or glass touches your lips, take exactly 10 large gulps before putting it down.
12 Healthy Bottled Water Brands
Cardiologists warn against drinking from plastic bottled water primarily due to microplastics, nanoplastics, and chemical additives. These contaminants are shed from the bottles themselves and can directly impact your cardiovascular health.
Ninety-five percent (95%) of the capital's drinking water is perfect, given the daily checks of chlorination at different treatment plants. However, weak infrastructure and climate change seriously threaten Mexico City's ability to provide its inhabitants with clean, sufficient water.
Although filters can be helpful in removing harmful chemicals from our water, they sometimes strip away beneficial minerals too. These include magnesium and calcium, as well as iron and manganese, which are eliminated to make water softer and prevent discolouration, respectively.
Below are some of the most common waterborne diseases:
The best time to drink water is consistently throughout the day, but key strategic moments maximize its benefits.
Weil's disease is a severe, life-threatening form of leptospirosis. The earliest signs—which appear suddenly, 2 to 14 days after infection—mimic the flu:
Waterborne diseases are caused by microscopic pathogens (bacteria, viruses, and parasites) that are ingested through contaminated drinking water or recreational water. The 7 most common include:
Common symptoms of bad drinking water include nausea, vomiting, diarrhea, and stomach cramps. These signs show that your water might be contaminated with bacteria, viruses, or harmful chemicals.
Coliform bacteria in drinking water
Coliform bacteria such as Escherichia coli are typical indicator organisms. They can only survive in drinking water for a few days – which is why their detection almost always points to a recent faecal contamination.
There is no single state with universally the "worst" tap water, as quality varies by utility. However, based on high contaminant counts, EPA violations, and population exposure, Texas and New Jersey consistently rank at the bottom.
Switzerland, Finland, and Iceland frequently tie for the cleanest tap water in the world, routinely earning a perfect 100 on the Yale Environmental Performance Index. These countries rely on pristine alpine sources, deep natural filtration, and rigorous testing.
Yes, Mexico owes the United States a significant amount of water. Under the 1944 Water Treaty, Mexico is required to deliver 1.75 million acre-feet of water to the U.S. every five years.
The #1 worst drinks for your heart are sugar-sweetened beverages (SSBs), such as regular sodas, sweetened fruit juices, sports drinks, and energy drinks. Cardiologists and medical bodies consistently rank these highest in danger due to their ability to drive up inflammation, blood pressure, triglycerides, and heart disease risk factors.
When shopping for the safest and cleanest bottled water, look for brands sourced from protected, pristine aquifers that consistently pass independent purity tests for heavy metals, microplastics, and forever chemicals (PFAS). Premium options in glass bottles or cartons generally perform best.
When your heart isn't pumping efficiently, it often sends subtle, "quiet" warning signals long before a major health crisis occurs.
Bottom line: for daily use go with Fiji or Evian, for purity choose Essentia, and for taste and minerals go with Mountain Valley. These are the worst waters we tested in 2026. First on our list is Topo Chico scoring 38 out of 100 due to it having the highest levels of forever chemicals or PFAS of any bottled water.
The top 5 bottled waters include:
Depending on your criteria, the "#1" water varies: Evian is frequently ranked as the top premium/cleanest bottled water, Fiji is the top pick for taste, and Aquafina is the highest-selling by volume. Generally, natural spring waters are considered the healthiest options.