Water quality statistics connect public health, infrastructure, and the condition of rivers, lakes, and wetlands. The figures below span global estimates, U.S. national assessments, and an older U.S. reporting cycle, so the measurement period and geography matter for every comparison.
Contents
- Drinking-water access and illness
- Waterborne outbreaks by source
- Global drinking water, sanitation, and hygiene
- U.S. drinking-water infrastructure
- Rivers and streams: biological condition
- Chemical, microbial, and habitat indicators
- Lakes, wetlands, and long-term context
Drinking-water access and illness
The CDC estimates that at least 1.1 million people in the United States get sick every year from germs in drinking water. The CDC describes that figure as about 1 in every 300 people in the country. These are national estimates rather than a local count, and they describe illness associated with germs in drinking water rather than every possible water-quality concern. (CDC Drinking Water Facts and Stats)
Access to a regulated system is also widespread. In the United States, 9 out of 10 people get their tap water from a regulated public water system, according to the CDC. That leaves a substantial population outside that particular arrangement, including people whose drinking water comes from private sources. (CDC Drinking Water Facts and Stats)
The CDC identifies Legionella as the most common cause of illness outbreaks linked to drinking water. For public tap-water outbreaks during 2010–2022, the CDC ranks Campylobacter second, Giardia third, Norovirus fourth, and Pseudomonas fifth. The ranking describes outbreak causes in that period; it is not a statement that each organism has the same prevalence in every community or year. (CDC Drinking Water Facts and Stats)
Waterborne outbreaks by source
The CDC gives a separate ranking for private drinking-water outbreaks during 2010–2022. Legionella was the most common cause in that category, followed by Norovirus in second place, E. coli in third, Cryptosporidium in fourth, and Giardia in fifth. Separating public tap-water and private drinking-water results is important because the two categories are not interchangeable. (CDC Drinking Water Facts and Stats)
| Ranking | Public tap-water outbreaks, 2010–2022 | Private drinking-water outbreaks, 2010–2022 |
|---|---|---|
| 1 | Legionella | Legionella |
| 2 | Campylobacter | Norovirus |
| 3 | Giardia | E. coli |
| 4 | Norovirus | Cryptosporidium |
| 5 | Pseudomonas | Giardia |
This outbreak ranking is one way to read water-quality statistics: the source category and time window define what the numbers mean. It should not be converted into a general ranking of all hazards in drinking water, because the CDC statements here concern illness outbreaks and their reported causes.
Global drinking water, sanitation, and hygiene
WHO estimated that 74% of the world’s population used safely managed drinking water services in 2024. In the same WHO data theme, 3.4 billion people lacked safely managed sanitation services in 2024, while 1.7 billion people lacked a handwashing facility with soap and water at home. These are global estimates for 2024 and cover related but distinct services. (WHO WASH data theme)
WHO and UNICEF said about 2.2 billion people gained access to safely managed drinking water between 2000 and 2024. The figure describes change over a 24-year period; it is not the number of people who lacked access at the end of 2024. (WHO Progress on household drinking water, sanitation and hygiene 2000–2024)
Earlier WHO monitoring figures provide another global reference point. WHO estimated that 27% of the global population, or 2.2 billion people, lacked safely managed drinking water in 2022. It also estimated that 43% of the global population, or 3.5 billion people, lacked safely managed sanitation in 2022, and that 25%, or 2.0 billion people, lacked a handwashing facility with soap and water at home. (WHO WASH monitoring)
The 2022 and 2024 figures should be read as estimates from their respective reporting periods, not as a single uninterrupted local series. They show that drinking-water access, sanitation, and household handwashing remain separate dimensions of water and public-health conditions.
U.S. drinking-water infrastructure
The EPA’s 7th Drinking Water Infrastructure Needs Survey and Assessment found that U.S. drinking-water systems will need $625 billion over 20 years. The EPA also said existing tribal drinking-water infrastructure needs exceed $4 billion over the next 20 years. These are infrastructure-need estimates, not measured spending totals or a forecast of a particular community’s bill. (EPA 7th DWINSA)
The same 7th DWINSA update estimated a total of 4 million lead service lines. A later EPA 2023 update supplied a more detailed national projection: 5,126,926 projected lead service lines nationwide before incorporating new inventory data, and 9,031,938 projected lead service lines after incorporating that new inventory data. Because the two lead-line figures use different update states, they should not be treated as a simple before-and-after replacement count. (EPA 7th DWINSA; EPA 2023 Update to the 7th DWINSA)
The EPA’s 2023 update also estimated 2,861,269 projected galvanized service lines nationwide, 88,289,166 projected not-lead service lines, 23,819,901 projected unknown service lines, and 14,476,490 unreported service lines. The update estimated 100,182,373 total service lines nationwide. These are projections and classifications in a national inventory update, not a direct inspection result for every line. (EPA 2023 Update to the 7th DWINSA)
| EPA infrastructure measure | National figure |
|---|---|
| Projected lead service lines, earlier update state | 5,126,926 |
| Projected lead service lines, after new inventory data | 9,031,938 |
| Projected galvanized service lines | 2,861,269 |
| Projected not-lead service lines | 88,289,166 |
| Projected unknown service lines | 23,819,901 |
| Unreported service lines | 14,476,490 |
| Total service lines | 100,182,373 |
Rivers and streams: biological condition
The EPA’s 2024 National Water Quality Inventory report said 28% of U.S. river and stream miles had healthy biological communities based on macroinvertebrates. The report also said 35% of U.S. river and stream miles were rated good by a fish-community index. These indicators measure different aspects of biological condition, so their percentages are not interchangeable. (EPA National Water Quality Inventory Report to Congress)
Several habitat measures were also reported for U.S. river and stream miles. The EPA said 68% were rated good for in-stream fish habitat, 56% had good riparian vegetation cover, and 57% had good streambed sediments. At the same time, 64% had moderate or high riparian disturbance. A site can therefore have a favorable result for one indicator and an unfavorable result for another. (EPA National Water Quality Inventory Report to Congress)
The report’s human-disturbance ratings divided U.S. river and stream miles into 36% good, 42% fair, and 22% poor. Those categories summarize the report’s disturbance indicator and should not be read as a complete rating of every chemical, biological, or recreational use. (EPA National Water Quality Inventory Report to Congress)
Chemical, microbial, and habitat indicators
Nutrient-related results were among the more concerning river and stream statistics in the EPA report. The EPA said 42% of U.S. river and stream miles were rated poor for excess phosphorus, while 44% were rated poor for excess nitrogen. These measures concern different nutrients, and the report does not support combining them into one percentage. (EPA National Water Quality Inventory Report to Congress)
Other indicators showed different patterns. The EPA said 98% of U.S. river and stream miles were not acidic, and 85% were in good condition for salinity. The report also said enterococci exceeded its benchmark in 20% of U.S. river and stream miles. Microcystins were detected in 9%, and cylindrospermopsin was detected in 10%. Detection or benchmark exceedance is specific to the stated indicator and does not establish that all sampled water was unsafe for every use. (EPA National Water Quality Inventory Report to Congress)
Fish-tissue results used a stated sample base. Mercury exceeded its fish-tissue criterion in 26% of the 41,099 river miles sampled for that indicator. Total PCB concentrations exceeded fish-tissue screening levels in 45% of the same 41,099 sampled river miles for that indicator. The sample base and the fish-tissue context are essential parts of both figures. (EPA National Water Quality Inventory Report to Congress)
Lakes, wetlands, and long-term context
The EPA’s national assessment rated lakes by human disturbance as 25% good, 45% fair, and 29% poor. For river and stream miles, the corresponding human-disturbance figures were 36% good, 42% fair, and 22% poor. Wetland area had a different distribution: 18% good, 44% fair, and 36% poor for human disturbance. These are separate ecosystem categories and should not be averaged. (EPA National Water Quality Inventory Report to Congress)
The EPA said 51% of lakes had high riparian vegetation cover, while 26% had low cover. It also reported that 95% of wetland area was in good condition in the 2018–2019 assessment. The wetland-area result is tied specifically to that assessment period, while the lake vegetation figures describe the lake indicator reported in the national inventory. (EPA National Water Quality Inventory Report to Congress)
An older benchmark shows why reporting year matters. EPA’s 2004 National Water Quality Inventory report said 44% of assessed stream miles were not clean enough to support uses such as fishing and swimming. It also said 64% of assessed lake acres and 30% of assessed bay and estuarine square miles were not clean enough to support uses such as fishing and swimming. These are legacy figures from the 2004 reporting cycle, and they are not presented here as independently verified current conditions. (EPA 2004 Reporting Cycle Profile)
Taken together, the statistics describe several distinct layers of water quality: access to drinking water, reported illness outbreaks, infrastructure condition, biological health, chemical indicators, habitat, and recreational-use support. The dates, geographic scales, and measurement definitions determine which comparisons are meaningful.