The old paint on your walls is probably harmless. Sanding it off is the dangerous part

Yesterday's advice about repainting a building ended, as it always does, with preparation: get the old surface sound before the new coating goes on. It is the right advice, and on a building painted before about 2017 there is a serious qualification attached to it that hardly anybody hears.

That old film may contain lead — potentially a great deal of it. And the film sitting quietly on the wall is not the hazard. The hazard is created at the moment somebody takes a power sander, a wire brush or a blowlamp to it, which is exactly what "preparing the surface properly" tends to mean.

Why paint had lead in it at all

Lead was not an impurity. It was added, deliberately, because it was extremely good at three jobs.

Pigment. Lead chromate gives brilliant, opaque yellows and oranges; lead oxides give reds. These pigments had superb hiding power, held their colour outdoors and were cheap for the coverage they gave.

Durability. Leaded films were tough, adhered well and stood up to weather, which is why lead concentrated in exactly the paints applied where durability mattered — exterior enamels, gates and grilles, window frames, doors, stair railings.

Drying. Lead compounds were used as driers in alkyd and oil-based paints, catalysing the oxidative cure that turns a wet film hard.

So the leaded paint in an Indian building is not randomly distributed. It is concentrated in the glossy enamel on metalwork and joinery, and in bright yellows, oranges and reds — which is also, uncomfortably, the palette of a lot of older painted furniture, playground equipment and school woodwork.

What the rule actually says

India regulated this in 2016. The Regulation of Lead Contents in Household and Decorative Paints Rules, notified under the Environment (Protection) Act, cap total lead in household and decorative paints at 90 parts per million, and came into force from 1 November 2017.

Ninety ppm is a strict limit — it is the same figure used in the strictest regimes internationally, and it is set low enough that it effectively means "no lead added". Compliant modern paint from a mainstream manufacturer is not the problem this article is about.

Two things about the rule are worth knowing precisely, because both are routinely misunderstood.

It is not retrospective. It governs paint manufactured and sold from that date. Every leaded film applied before it is still on the wall, and buildings do not repaint themselves. Given India's housing stock, the quantity of pre-2017 paint in place is enormous.

It covers household and decorative paints. Industrial coatings — road marking, structural steel, marine and certain specialist products — sit outside that particular limit. This matters most for anyone reusing industrial materials domestically, which happens more often than it should.

For a sense of the gap the rule closed: testing of Indian enamel paints in the years before it repeatedly found samples orders of magnitude above 90 ppm, with the worst results in bright yellows and reds. The rule was a real intervention, not a formality — which is precisely why what came before it deserves respect.

The exposure route almost nobody expects

Here is the part that changes what you should actually do.

Lead in an intact, well-adhered, painted-over film is largely going nowhere. It is bound in a polymer matrix on a wall. Nobody is eating the wall. A sealed old film under a modern coat of emulsion is, in public health terms, a reasonably well-managed hazard.

The hazard is dust. Lead becomes available when the film is disturbed and turned into fine particles that settle on floors, sills, food surfaces and hands. Three situations do that:

Renovation. Dry power-sanding, wire-brushing, scraping and — worst of all — burning off with a blowlamp or heat gun. Torching leaded paint volatilises lead and produces fume, which is the single most dangerous way to remove it. Dry abrasive blasting is comparably bad. A weekend of enthusiastic surface preparation can contaminate a home more thoroughly than decades of the paint simply sitting there.

Friction and impact surfaces. Windows that slide in painted frames, doors that rub, drawer runners, stair rails and gates. These grind their own paint into powder continuously, without anybody doing anything. In older housing, painted window channels are a classic and well-documented lead dust source.

Deteriorating paint. Flaking, chalking and peeling film sheds chips and powder, particularly at low level where small children reach. Paint chips are also mildly sweet-tasting, which is an unpleasant piece of chemistry that has been a factor in childhood poisoning for a century.

Notice that all three are more about the condition and disturbance of the film than about its lead content in the abstract. That is the practical insight the entire subject turns on.

Why children, specifically

The risk is not evenly shared, and the difference is not marginal.

Small children absorb a substantially larger fraction of ingested lead than adults do, and their behaviour maximises exposure — hands on floors, hands in mouths, playing at the exact height where paint chips and settled dust accumulate. Lead crosses into the developing nervous system, where its effects are on cognition, attention and behaviour, and those effects are not reversed by later removal of the exposure.

Two facts define the seriousness. There is no identified safe blood lead level in children — the health agencies that set reference values have repeatedly lowered them as evidence accumulated at lower and lower concentrations, which is the signature of a threshold nobody can find. And the harm is silent: there is no acute illness at the levels that matter, nothing a parent would notice, and the effect shows up only as a child who does slightly less well than they would have.

The scale in India is significant. A widely cited 2020 assessment estimated that a very large number of Indian children carry blood lead above the reference level used at the time. Paint is one contributor among several — lead-acid battery recycling, some adulterated spices, certain cookware and cosmetics all feature — and honesty requires saying that paint is not the largest source everywhere. But it is the one sitting inside the home, and it is the one that a renovation decision can make dramatically worse in a single afternoon.

The intact film on your wall is a managed hazard. The decision to sand it is what converts it into an exposure. Almost everything protective about lead paint management follows from that one sentence.

Leave it, seal it, or take it off

Given that, the hierarchy of responses is not the intuitive one.

Leave it alone if it is intact and in a place nobody disturbs. Sound, adherent paint that is not on a friction surface and is not accessible to a small child is best monitored, not attacked. This is a legitimate answer, not an evasion.

Encapsulate. Sealing the old film under a new coating that bonds well and is maintained is a recognised, low-disruption treatment — this is where a coating stops being the problem and becomes the remedy. Two conditions matter. The old film must be sound enough to hold the new one; encapsulating flaking paint just buys a delay. And it must be maintained, because an encapsulant that fails re-creates exactly the situation it was hiding. It is also not appropriate on friction surfaces, where the new film will simply be ground away with the old.

Enclose. Cladding or a new component over the painted one — new window frames, a panel over a painted surface — physically separates the film from the room.

Remove, carefully, when the paint is deteriorating, on a friction surface, or where a building's use has changed to something involving small children. Removal is the most protective option and the one that generates the exposure, which is why how it is done matters more than whether it is done.

If removal is the answer, the practices are specific and not optional:

• No dry power sanding, and no burning. A heat gun or blowlamp on leaded paint is the worst available method. If mechanical tools are used at all, they should be fitted with HEPA-filtered dust extraction.
• Wet methods. Misting the surface and wet-scraping suppresses airborne dust dramatically, and it costs nothing.
• Containment. Plastic sheeting on floors and over doorways; keep children, pregnant women and food out of the area entirely for the duration.
• Chemical strippers rather than abrasion where practical, with the waste collected rather than washed into drains.
• Wet cleanup. Wet wiping and HEPA vacuuming, not sweeping. Sweeping redistributes exactly the particle size that matters.
• Personal hygiene. Change clothes, wash before eating, and do not carry work clothing into living areas — this is the same take-home pathway that has been documented in industrial lead work for decades.

Testing exists and is worth knowing about: handheld XRF analysers read lead in a film in place without damaging it, and laboratories will analyse paint chips. Before a large renovation on an old building — and certainly before one in a school, crèche or paediatric facility — the test is cheap relative to the decision it informs.

Where this connects to everything else

Two threads from earlier in this series run straight through it.

The first is that this is now the fourth time the same story has appeared in coatings chemistry: a substance is adopted because it is genuinely excellent at a physical job, its toxicity catches up with it, and the industry has to find a replacement that is never quite as good at first. Lead in paint, chromate in corrosion primers, bisphenol A in can linings, fluorochemicals in textile finishes. The pattern is consistent enough to be predictive, and the sensible conclusion is not that coatings are dangerous — it is that "we have used this for decades and it is fine" has a poor track record as an argument.

The second is that this is the reason surface preparation deserves more thought than it gets. Yesterday's article argued that preparation decides whether a paint job lasts. This one adds that on an old building, preparation also decides whether a paint job is safe. Both point at the same neglected half-day of work at the start of the project.

Why it matters for students and researchers

There is more accessible, useful work in this area than its low profile suggests.

The most valuable is unglamorous exposure mapping: which building stock, which surfaces and which renovation practices actually drive childhood lead exposure in Indian cities, disentangled from the other sources. The policy question — where does an intervention rupee do the most good — cannot be answered without that, and it is field work rather than expensive instrumentation.

On the materials side, encapsulant performance is genuinely under-studied. How long does a sealing coat reliably contain an underlying leaded film under Indian temperature and humidity cycling; what adhesion and flexibility properties predict that; and how should such a product be specified and verified? These are answerable questions with an immediate public-health payoff.

There is also an instrumentation opening: low-cost field screening for lead in paint. XRF units are effective and expensive. A cheaper screening method with acceptable sensitivity, usable by municipal staff rather than specialists, would change what is possible at scale — and analytical chemistry departments are well placed to attempt it.

And there is a straightforward compliance question worth someone's time: post-2017 market surveillance. Are paints on sale meeting 90 ppm, including in the informal and small-manufacturer segment? Periodic independent testing is exactly the kind of work a university group can do credibly, and it is how a good regulation is kept honest.

Frequently asked questions

How do I know if my old paint has lead?

You cannot tell by looking, and colour is a hint rather than an answer — bright yellows, oranges and reds, and glossy enamel on metal and joinery, are the higher-probability cases. Age is the strongest signal: paint applied before about 2017 in India predates the limit. Definitive answers come from an XRF reading taken in place or laboratory analysis of a chip, and before a major renovation of an older building that test is worth doing.

Is it safe to live in a house with lead paint?

Generally yes, if the paint is intact and maintained. Sound, well-adhered film that nobody is sanding, and that is not on a rubbing surface, presents little exposure. What changes the picture is deterioration, friction surfaces, and renovation. Practical measures are mundane and effective: keep painted surfaces in good repair, wet-mop floors and window sills rather than sweeping, wash children's hands before meals, and keep toys off floors where paint dust may settle.

Can I just paint over it?

Often yes, and it is frequently the better choice. Encapsulation under a sound, maintained coating is a recognised treatment. The conditions are that the existing film must be stable enough to support the new one, the new coating must be maintained rather than forgotten, and it is not suitable on friction surfaces where both films will be ground to powder. Painting over flaking paint is not encapsulation; it is a delay.

Is modern paint safe?

Household and decorative paint manufactured for the Indian market after the rule came into force is capped at 90 ppm total lead, which is effectively no added lead, and reputable manufacturers state compliance. The residual caution is for industrial coatings, which sit outside that particular limit, and for informal or unbranded product where compliance is harder to verify. If a modern paint is being used somewhere a child will be, buying from a manufacturer that publishes its compliance is a reasonable precaution.

What is the single most dangerous thing to do with old paint?

Burning it off with a heat gun or blowlamp, and dry power-sanding a close second. Both convert a stable film into inhalable fume or fine dust in the space of an afternoon, in an enclosed room, usually with the family still living there. If you take one thing from this article, it is that these two methods should never be used on paint that predates the limit.