Arsenic exposure statistics span global drinking-water guidance, large Bangladesh well surveys, historical high-exposure cohorts, health outcomes, and prevention programs. The figures below distinguish measured observations from surveys, forecasts, and regulatory estimates.
Key Arsenic Exposure Statistics
The most broadly useful figures are:
- WHO’s global drinking-water guideline is 10 µg/L (10 ppb) under its current assessment.
- Millions of people are exposed to drinking water containing at least 100 µg/L arsenic according to WHO’s current global assessment.
- EPA’s U.S. maximum contaminant level is 10 µg/L (10 ppb) for covered public water systems under the final rule.
- EPA estimated that lowering U.S. arsenic from 50 to 10 µg/L would protect about 13 million Americans served by community and non-transient non-community systems.
- 72% of wells exceeded 10 µg/L in the early-2000s HEALS rural Bangladesh study areas.
- 52% of wells exceeded 50 µg/L in those same early-2000s HEALS study areas.
- 4.94 million Bangladesh tube wells were tested from 2000 to 2003 in a national testing campaign.
- 26% of tested Bangladesh wells exceeded 50 µg/L in 2021–2023, compared with 41% in the earlier survey summarized by a later analysis.
- An estimated 22–23 million people in Bangladesh were exposed above 50 µg/L in 2021–2023, down from about 30–33 million in 2000–2005.
- More than 70% of functioning Matlab tubewells exceeded 10 µg/L in 2002–2003.
- 504 arsenic-related skin-lesion cases were identified among 166,934 people in Matlab from January 2002 through August 2003.
- A Bangladesh model projected about 1.2 million future hyperpigmentation cases under continued exposure assumptions in a projection published in 2003.
- 37% of households receiving a 2018 information intervention reported changing water source or treatment, compared with 10% in the comparison group in Phulsara Union.
- Mean arsenic fell from 170 to 76 µg/L among 63 Phulsara households that changed source during the 2018 intervention.
- Median urinary arsenic fell from 117 to 51 µg/L within one week in a six-month Araihazar household-filter study.
- EPA estimated annual U.S. arsenic-rule compliance costs at $181 million in its rule-era analysis.
- EPA estimated $140–$198 million in quantified monetized benefits for the U.S. arsenic rule, in 1999 dollars.
Contents
- Key Arsenic Exposure Statistics
- Worldwide Arsenic Exposure Statistics and Drinking-Water Thresholds
- Bangladesh Well Testing and Exposed Populations
- Arsenic Concentrations and Geographic Variation
- Health Outcomes, Skin Lesions, and Mortality Data
- Testing, Water Switching, and Treatment Outcomes
- Regulation Costs and Quantified Benefits
Worldwide Arsenic Exposure Statistics and Drinking-Water Thresholds
The central comparison is between a concentration guideline and the populations or systems measured against it. WHO’s current drinking-water recommendation is 10 µg/L, or 10 parts per billion, but describes the value as provisional because practical removal difficulties remain.
WHO also reports that millions of people are exposed at concentrations of 100 µg/L or higher globally. See WHO’s Arsenic fact sheet.
| Standard or estimate | Figure | Scope and period |
|---|---|---|
| WHO drinking-water guideline | 10 µg/L | Global, current guideline |
| WHO reported high exposure | Millions of people at or above 100 µg/L | Global, current assessment |
| EPA maximum contaminant level | 10 µg/L | U.S. covered public systems, final rule |
| EPA population protected by 50-to-10 µg/L reduction | About 13 million people | U.S. final-rule estimate |
EPA’s 10 µg/L maximum contaminant level applies to covered U.S. public water systems, not every private well. EPA estimated that reducing arsenic from 50 to 10 µg/L would protect about 13 million Americans served by community and non-transient non-community systems, using the systems and baseline assumptions in its final-rule analysis (EPA Technical Fact Sheet).
Thresholds are not interchangeable across studies. WHO and EPA use 10 µg/L, while several Bangladesh studies report against the historical 50 µg/L national standard.
Bangladesh Well Testing and Exposed Populations
Bangladesh provides some of the largest measured well and population datasets in this evidence set. In the early-2000s HEALS rural study areas, 72% of wells exceeded 10 µg/L and 52% exceeded 50 µg/L, but these are study-area results rather than current national prevalence estimates (Reduction in exposure to arsenic from drinking well-water in Bangladesh).
A national campaign tested 4.94 million tube wells between 2000 and 2003. A later peer-reviewed analysis compared 4.7 million wells in a 2000–2005 survey with 6.3 million wells tested during 2021–2023; the programs and field methods were not necessarily identical (Low-cost informational intervention reduced drinking water arsenic exposure in Bangladesh).
| Bangladesh well-survey comparison | 2000–2005 | 2021–2023 |
|---|---|---|
| Wells tested | 4.7 million | 6.3 million |
| Wells above 50 µg/L | 41% | 26% |
| Estimated population above 50 µg/L | About 30–33 million | About 22–23 million |
| Unions with more than 80% of wells above 50 µg/L | 357 | 165 |
The later analysis estimated that the population exposed above 50 µg/L fell from about 30–33 million to 22–23 million across the two survey periods. It also counted 357 unions with more than 80% of wells above 50 µg/L in the earlier survey and 165 in the later one; Bangladesh had approximately 4,600 unions in the administrative system used by that analysis.
These are cross-survey comparisons, and the population figures are extrapolations rather than direct censuses (Low-cost informational intervention reduced drinking water arsenic exposure in Bangladesh).
In Araihazar, researchers tested 5,967 contiguous tube wells and collected arsenic-exposure and demographic data from 65,876 well users. During the study fieldwork, 54% of residents regularly consumed well water at or above 50 µg/L; 92% said they were willing to take steps to reduce exposure, while 46.2% preferred switching to a safe well.
Willingness and preference were self-reported and do not establish completed exposure reduction (Prevalence of arsenic exposure from drinking water and awareness of its health risks).
Arsenic Concentrations and Geographic Variation
Well concentrations varied sharply within Bangladesh study areas. In Matlab during 2002–2003, sampled tubewells ranged from below 1 to 3,644 µg/L, and more than 70% of functioning tubewells exceeded the WHO 10 µg/L guideline (Prevalence of arsenic exposure and skin lesions).
Phulsara Union also showed a wide distribution. In 2018, arsenic in 481 household-water sources ranged from below 0.7 to 650 µg/L, with a mean of 107 µg/L; 50% of samples were below 50 µg/L, which does not necessarily mean they were below the WHO guideline.
A compiled 2005 dataset covering 2,213 wells had a mean of 69 µg/L, with 46% below 50 µg/L (Low-cost informational intervention reduced drinking water arsenic exposure in Bangladesh).
| Location and period | Measured concentration result | Definition |
|---|---|---|
| Matlab, 2002–2003 | Below 1–3,644 µg/L | Sampled tubewells |
| Phulsara, 2018 baseline | Below 0.7–650 µg/L; mean 107 µg/L | 481 household sources |
| Phulsara, 2005 | Mean 69 µg/L | 2,213 wells |
| Rural Bangladesh, early 2000s | Mean 180 ± 140 µg/L | 956 existing village wells |
A rural Bangladesh community-well study found that existing village wells averaged 180 ± 140 µg/L. Five of six newly installed deep community wells stayed within the WHO 10 µg/L guideline during 4–11 months of monthly sampling, while one met Bangladesh’s 50 µg/L arsenic standard but exceeded WHO guideline values for manganese and uranium; arsenic compliance therefore did not establish overall water safety (Community wells to mitigate the arsenic crisis in Bangladesh).
Historical cohorts illustrate why geography and period matter. About 125,000 Antofagasta residents were exposed to 860 µg/L from the city’s only water source until 1970; cited cohorts included 8,251 participants above 600 µg/L in southwestern Taiwan, 698 people above 300 µg/L in northeastern Taiwan, 902 people drinking above 500 µg/L in West Bengal, and 10,430 participants above 300 µg/L in rural Matlab, Bangladesh (Age at Exposure to Arsenic in Water and Mortality 30–40 Years After Exposure Cessation).
These are historical study cohorts, not current prevalence estimates.
Health Outcomes, Skin Lesions, and Mortality Data
In Matlab, screening from January 2002 through August 2003 identified 504 arsenic-related skin-lesion cases among 166,934 people aged over four years, a crude prevalence of 3 per 1,000. The highest skin-lesion prevalence occurred in the 35–44 age group for both sexes, and men had a standardized mortality ratio of 158 for skin lesions, with a 95% confidence interval of 133–188; that statistic is a sex comparison, not a general cancer mortality rate (Prevalence of arsenic exposure and skin lesions).
A Bangladesh geostatistical and epidemiologic model published in 2003 projected the following outcomes under continued exposure assumptions:
- About 1.2 million future hyperpigmentation cases.
- About 600,000 keratosis cases.
- About 125,000 skin-cancer cases.
- About 3,000 deaths per year from internal cancers.
These are forecasts based on modeled exposure distributions and dose-response assumptions, not observed case counts; later mitigation may not match the continuation assumptions (Age at Exposure to Arsenic in Water and Mortality 30–40 Years After Exposure Cessation).
Testing, Water Switching, and Treatment Outcomes
Information, testing, source switching, and filters produced different measured outcomes in Bangladesh studies. In Phulsara Union during 2018–2019, 37% of households receiving the first information intervention reported changing water source or treatment, compared with 10% in the comparison group.
The result was self-reported and localized rather than a universal treatment effect (Low-cost informational intervention reduced drinking water arsenic exposure in Bangladesh).
- 32% of households accepted free testing of an additional source, and 53% of that subset changed source.
- Among 63 intervention households that changed source, mean arsenic fell from 170 to 76 µg/L.
- In the same 63 households, median arsenic fell from 167 to 41 µg/L.
- Intervention households had drinking-water arsenic levels averaging 64% lower than untreated comparison households.
Two years after a national campaign, 27% of Araihazar households had switched away from their tested well, but switching did not always mean moving to a tested safe well. At follow-up, 21% did not know their well’s arsenic status, and 21% of unsafe-well households that switched moved to an untested well (Reduction in exposure to arsenic from drinking well-water in Bangladesh).
In a fee-based testing trial, 93% of eligible households in the two education intervention groups bought an arsenic test, compared with 53% in the control group. Purchase established testing behavior, not necessarily safe water use (Reduction in exposure to arsenic from drinking well-water in Bangladesh).
A six-month household-filter study in Araihazar found median urinary arsenic fell from 117 to 51 µg/L within one week, then rose to 126 µg/L by the end of the trial. Urinary arsenic is a recent-exposure biomarker; total urinary arsenic can include less-toxic organic arsenic from seafood, so it does not by itself identify the exposure source or chemical form (Provision of well-water treatment units to 600 households in Bangladesh).
Community wells supplied an average of 2,200 litres per day by hand pumping during one year of monitoring, and each well was estimated to meet the needs of about 500 people within a 150-metre radius. These were planning estimates from six selected wells in densely populated rural Bangladesh (Community wells to mitigate the arsenic crisis in Bangladesh).
Arsenic Drinking-Water Regulation Costs and Quantified Benefits
EPA’s final-rule analysis estimated $181 million in annual national compliance costs in 2000 dollars: $177 million for treatment, $2.7 million for monitoring and administration, and $1.0 million for state costs. EPA estimated average annual household cost at about $32 for approximately 2,387 community systems requiring treatment (EPA Technical Fact Sheet).
| U.S. community-system size | EPA estimated annual household cost |
|---|---|
| 25–500 people | $327–$162 |
| 501–3,300 people | $71–$58 |
| 3,300–10,000 people | $38 |
| 10,000 or more people | $32–$0.86 |
These are historical rule-era estimates, and the ranges reflect system size and economies of scale rather than current prices. EPA’s quantified monetized benefits were estimated at $140–$198 million in 1999 dollars, excluding substantial non-quantified benefits.
EPA estimated that reducing arsenic from 50 to 10 µg/L would prevent about 19–31 bladder-cancer cases and 5–8 bladder-cancer deaths per year. The same reduction was estimated to prevent about 19–25 lung-cancer cases and 16–22 lung-cancer deaths per year; these are model-based benefits limited to the rule’s quantified risk-assessment scope, not observed post-rule counts (EPA Technical Fact Sheet).