A borewell can pour out water that looks glass-clear, tastes clean, and still carry a slow poison you have no way to notice. Arsenic in borewell water has no colour, no smell, and no taste, which is exactly what makes it so risky in the districts where it hides. You will not get a warning sign at the tap.
I am Arjun, and after 15 years running my own borewell, pump, and overhead-tank setup, arsenic is the one thing I stopped trying to judge by eye a long time ago. In this primer I will show you where arsenic comes from, which regions are affected, what a safe limit really means, how to test properly, and what to do if your water fails. For the bigger picture, our complete guide to water testing and quality ties it all together.
Key Takeaways
- Arsenic is invisible, tasteless, and odourless, so the only way to know your level is a proper test.
- The common safe limit for drinking water is 0.01 mg/L (10 parts per billion), the value used by BIS and the WHO.
- In India the biggest hotspots are the Ganga and Brahmaputra plains: parts of West Bengal, Bihar, Uttar Pradesh, Assam, and Jharkhand.
- Cheap field kits struggle near the safe limit. A certified lab is the number you can actually trust.
- Boiling does not remove arsenic. It concentrates it, so you need the right treatment instead.
What arsenic in borewell water really is
Arsenic is a natural element locked inside certain rocks and sediments. In many affected areas it is not dumped by a factory: it leaches into groundwater on its own, out of the same alluvial layers your borewell draws from. This is called geogenic contamination, and it is why a well far from any industry can still test high.
Because arsenic dissolves invisibly, your senses are useless here. Clear, sweet-tasting water can sit well above the safe limit. That single fact is the reason arsenic gets missed for years while a family keeps drinking it, and it is why testing is not optional in a known hotspot.
It also tends to hide at specific depths. In several Indian belts the worst readings come from shallow-to-mid alluvial aquifers, so two borewells on the same street, drilled to different depths, can give very different results.
Which areas have arsenic in groundwater?
Arsenic in groundwater is a well-documented problem across the Ganga and Brahmaputra river plains, and neighbouring Bangladesh has some of the most affected wells in the world. If you live in or near these belts, treat arsenic as a real possibility until a test says otherwise.
| Region | Why the risk is higher | What to do |
|---|---|---|
| Ganga plains (West Bengal, Bihar, eastern UP) | Arsenic-rich alluvial sediments in shallow aquifers | Test before trusting any new or existing borewell |
| Brahmaputra valley (Assam) | Similar young river-deposited sediments | Lab test, then retest deeper alternatives |
| Parts of Jharkhand, Chhattisgarh, Punjab, Manipur | Localised pockets reported by surveys | Check district data, then test your own well |
| Outside known belts | Lower baseline risk, but not zero | Include arsenic in a first-time full panel |
District-level data matters because contamination is patchy. India’s Central Ground Water Board publishes groundwater quality reports that can tell you whether arsenic has turned up near you. Use that as a first filter, then confirm with your own sample, because a neighbour’s clean result does not guarantee yours.
What arsenic does to your health
The danger with arsenic is not a quick stomach upset. It is long-term, low-dose exposure over years that causes harm, which is exactly why people ignore it for so long. There is no bad taste to warn a family off the water.
Chronic exposure is linked to skin changes such as dark patches and hard, thickened skin on the palms and soles, a pattern doctors call arsenicosis. Over longer periods it is associated with a higher risk of skin, bladder, and lung cancers, along with effects on the heart and, in children, on development. The exact risk depends on the level and how many years you drink it.
I am not a doctor, and this article cannot diagnose anyone. If you have been drinking untested borewell water in a hotspot, or you already see skin symptoms, speak to a qualified medical professional and get the water tested at a certified lab. To understand what else might be riding along in your supply, our beginner walk-through of what is actually in your well water is a good companion read.
What arsenic level is safe to drink?
The number to remember is small. The WHO guideline value and the Indian BIS acceptable limit for arsenic in drinking water are both 0.01 mg/L, which is the same as 10 micrograms per litre or 10 parts per billion. There is no known level that is completely risk-free, so lower is always better.
| Standard | Arsenic limit | Notes |
|---|---|---|
| BIS acceptable limit (IS 10500) | 0.01 mg/L | The target for safe drinking water |
| BIS permissible limit (no alternate source) | 0.05 mg/L | A fallback ceiling, not a green light |
| WHO guideline value | 0.01 mg/L | Same 10 ppb figure used worldwide |
Two quick cautions on reading a report. First, watch the units, because 0.01 mg/L, 10 µg/L, and 10 ppb are the same thing written three ways. Second, treat the higher 0.05 mg/L permissible figure as an emergency ceiling for when nothing else is available, not as a safe target to aim for.
How to test water for arsenic
Arsenic is harder to test well than something like TDS or hardness, because the safe limit is so low that cheap tools struggle to read it accurately. Here is the approach I would use, in order.
- Check your local groundwater data first. Look up your district on CGWB or state groundwater reports to see whether arsenic has been flagged nearby. This tells you how seriously to treat the test.
- Decide between a field kit and a lab. Arsenic field test kits are useful for a rough screen, but many are unreliable close to the 0.01 mg/L limit and can read falsely low. For a decision that affects health, go to a lab.
- Use the lab’s own bottle. Collect from a tap you have run for one to two minutes so you sample fresh borewell water, not water sitting in the pipe or tank. Fill to the line and cap with no air gap.
- Ask for total arsenic in mg/L. Request the result in a clear unit and, if offered, ask whether they can note the arsenic form, since that affects which treatment works best.
- Test other contaminants together. While you are at it, ask for iron and a basic panel, because iron chemistry interacts with arsenic removal and the sample is already collected.
- Record the result and retest. Note the value and date, and plan to retest at least once a year, or sooner if you deepen the well or a nearby well changes.
Tip: In my experience a certified lab arsenic test in India usually costs somewhere in the range of ₹500 to ₹1,500 per sample, far less than months of drinking a contaminated well. When a result sits anywhere near the limit, I pay for a second lab test rather than trusting a single reading.
What to do if your borewell has arsenic
If a lab confirms arsenic above the limit, stop using that water for drinking and cooking straight away and switch to a safe source while you plan a fix. The good news is that arsenic is treatable, but only with the right method for your water.
- Reverse osmosis (RO): a well-maintained RO system reduces arsenic effectively at the tap and is a common home choice.
- Activated alumina and iron-based adsorption media: designed specifically to pull arsenic out, often used for larger or whole-supply needs.
- Oxidation before filtration: some arsenic forms are harder to remove, so a treatment step that converts it first improves results.
- What does not work: boiling (it concentrates arsenic), plain carbon filters, and ordinary water softeners.
Whatever you install, the golden rule is to retest the treated water. A system on paper is not the same as a system working, so confirm with a fresh lab sample before you trust it for drinking.
For authoritative background, the World Health Organization and India’s Bureau of Indian Standards both publish the drinking-water limits referenced here. Since arsenic often shares a supply with other issues, it is worth pairing this with routine checks like our step-by-step on how to test well water for bacteria and coliform and how to test well water for nitrates.
Frequently Asked Questions
Which areas have arsenic in groundwater?
In India the main hotspots are the Ganga and Brahmaputra river plains, including parts of West Bengal, Bihar, eastern Uttar Pradesh, Assam, and Jharkhand, with localised pockets elsewhere. Neighbouring Bangladesh is heavily affected too. Contamination is patchy, so check district data and then test your own borewell.
How do you test water for arsenic?
Field test kits give a rough screen but are unreliable near the low safe limit. For a health decision, send a sample to a certified lab, collected in their bottle from a tap you have run for a minute or two. Ask for total arsenic reported in mg/L.
What arsenic level is safe to drink?
The widely used safe limit is 0.01 mg/L, which equals 10 micrograms per litre or 10 parts per billion. Both the WHO and Indian BIS use this figure. A higher 0.05 mg/L permissible limit exists only as a fallback when no alternate source is available, not as a safe target.
Does boiling remove arsenic from water?
No. Boiling kills bacteria but does the opposite for arsenic. As water evaporates, the arsenic that stays behind becomes more concentrated. To actually lower arsenic you need reverse osmosis, activated alumina, or a dedicated adsorption system, followed by a retest to confirm it worked.
Can I taste or smell arsenic in my well water?
No, and that is the core danger. Arsenic has no colour, taste, or smell, so water at unsafe levels looks and tastes perfectly normal. The only reliable way to know is a lab test. Clear water is never proof that a borewell in a hotspot is arsenic-free.
Where that leaves you
Arsenic is a quiet risk: no warning at the tap, harm that builds over years, and a safe limit small enough that guesswork is useless. If you live in or near a known hotspot, the sensible move is simple. Check your district data, get one certified lab test, and act on the number rather than on how the water looks.
Want to build a proper testing routine that covers arsenic alongside everything else in your supply? Start with our complete homeowner’s guide to water testing and quality, which turns scattered tests into one clear, yearly plan.
