Lead is a chemical chameleon. It resembles calcium so closely that the body takes it up as if it were a nutrient, and precisely where calcium is needed, in the nervous system and in the bones, it does its damage. At ETH Zürich we used lead isotopes as geological clocks: the ratio of the lead isotopes reveals the age of a rock. The same analysis answers a different question in a building, namely whether lead is present in paints, pipes and dust.
Where lead occurs in buildings
Three sources are typical, especially in buildings up to the 1970s:
- Lead paints: lead white (lead carbonate) in light-coloured paints, red lead (orange) as rust protection on metal, lead chromate in yellow and green tones. In Gründerzeit and Art Nouveau buildings they often lie beneath several newer layers. Intact, they are unproblematic; the risk arises when they flake or when work raises dust.
- Lead pipes: lead water pipes are found above all in the oldest building stock. The City of Vienna locates the main problem in the lead installations of Gründerzeit buildings, constructed up to 1938; the lead house-connection pipes there were replaced by 2007, yet in many old buildings the pipes inside the apartment were left in place, so that the last stretch to the tap can still be lead.
- Lead dust: the underestimated source. Weathering lead paint produces fine dust that accumulates on window sills, floors and in cracks, especially relevant in households with small children.
A brief look at the history
Lead pigments are ancient. Lead white, chemically basic lead carbonate, was the most important white pigment of all until the end of the 19th century (ColourLex); red lead, the orange-red lead oxide, served as a rust-protective primer directly on iron and steel, and lead chromate, as chrome yellow, supplied strong yellow tones (IARC 2006). Their toxicity was recognised early: as far back as 1921 the International Labour Organization adopted Convention No. 13, the so-called Geneva White Lead Convention, which obliged ratifying states to prohibit lead white and lead sulphate in the interior painting of buildings (with narrow exceptions). Austria ratified on 12 June 1924.
Over the course of the 20th century, lead white disappeared from paintwork: national bans and restrictions clustered between 1905 and 1930, and lead white was replaced by less toxic white pigments such as zinc white and titanium white (ColourLex). At European level, lead carbonates and lead sulphates were later restricted as a paint constituent, today under the REACH Regulation, with an exception now only for the restoration of works of art and historic buildings, which refers explicitly to that ILO convention of 1921. What sits in the layers of a particular old building therefore depends strongly on its construction age and on later renovations.
Why lead is dangerous
Lead is a neurotoxin. It disrupts signal transmission and the development of the brain. Babies and children under about six are most strongly affected, because their nervous system is still developing and they absorb a considerably higher proportion of ingested lead than adults do; impairments of intelligence, attention and behaviour are described. In adults, the main concerns are high blood pressure and kidney damage. According to the WHO there is no safe threshold: even small amounts are considered harmful. The IARC of the WHO classifies inorganic lead compounds as probably carcinogenic (Group 2A) and metallic lead as possibly carcinogenic (Group 2B).
Recognising lead pipes
A lead pipe can be identified visually by several features: it is grey and matt, soft (a key easily leaves a notch, a fresh scratch gleams silver), sounds dull when tapped, is not magnetic, and the joints are bead-soldered rather than screwed. Such pipes are most likely found at the house connection in the basement, on the riser pipes and on the last metres under the sink or washbasin. Important: this is only the visual identification. How much lead actually passes into the water is told only by an analysis.
How to determine lead reliably
The lead content of paint, plaster or dust cannot be judged with the naked eye. The reliable method is laboratory analysis by an accredited laboratory. For drinking water a stagnation sample is examined, that is, water taken after a defined standing time, because the lead concentration is highest after standing for longer. For paint, plaster and solder joints, material samples are evaluated layer by layer, and for dust, wipe samples. Sampling it yourself is not advisable, especially with lead paint: anyone scratching or sanding suspect paint creates exactly the lead-containing dust they want to avoid. Such work, and the sampling, require expertise and protective measures.
The legal framework
The Austrian Drinking Water Ordinance sets the parameter value for lead at 5 µg/l (0.005 mg/l). For water under § 4 Z 1 and 3 of the ordinance that value must be met by 12 January 2036 at the latest; until then a parameter value of 10 µg/l (0.01 mg/l) applies there. Both values transpose the EU Drinking Water Directive (EU) 2020/2184. Since lead pipes often fail to meet even the transitional value after longer stagnation, in practice the lower limit means replacing all lead pipes.
For the proper removal of lead-containing paints, the relevant occupational-safety and hazardous-substance rules apply. For old paint itself, by contrast, neither Austria nor Germany has a statutory threshold above which a coating counts as "lead paint" or as requiring remediation. Other countries draw the line differently: the United States define "lead-based paint" from 0.5 percent by mass or 1.0 milligram per square centimetre, France from 1 milligram per square centimetre. Which limits actually apply, where the frequently cited 0.3 percent comes from, and what a particular laboratory value means, is set out in detail in our article When is a coating lead paint?.
What to do
- Lead paint, intact: document and take into account at the next renovation. Do not sand, flame off or strip without protective measures. Painting over or sealing (encapsulation) is often the simplest solution.
- Lead paint, flaking, with children in the household: action needed. Professional removal or sealing by a specialist firm.
- Lead pipes: replacement is the only lasting solution; filters and coatings do not solve the problem. Until then the usual precautions apply: let the water run before use, use only cold water for cooking and drinking (warm dissolves more lead), and no water from lead pipes for baby food.
- Lead dust: wipe up damp rather than sweeping (sweeping spreads the dust), and eliminate the source.
Lead is not the only invisible pollutant in old buildings. Radon too can be neither seen nor smelled, and in buildings from before 1990 it is worth looking for asbestos.
Sources
- Drinking Water Ordinance (RIS): ris.bka.gv.at; EU Drinking Water Directive (EU) 2020/2184
- City of Vienna, "Blei im Trinkwasser" (lead installations mainly in Gründerzeit buildings constructed up to 1938; house-connection pipes replaced by 2007, in-apartment installations the owners' responsibility): wien.gv.at
- WHO, lead and health (no safe threshold, risk to children; in adults raised blood pressure and kidney damage): who.int. IARC: inorganic lead compounds Group 2A (Monograph Vol. 87, 2006), metallic lead Group 2B (Monograph Vol. 23/Supplement 7, 1987)
- German Environment Agency (UBA), „Blei im Trinkwasser ist gesundheitsgefährdend" (damage to the developing nervous system in children, impairment of blood formation and cognitive development, harmful even at very low intakes): umweltbundesamt.de
- History of lead pigments: ILO Convention No. 13 "White Lead (Painting) Convention" (1921), ratified by Austria on 12 June 1924 (ILO NORMLEX); IARC Monographs Vol. 87 (2006, red lead as rust protection, lead chromate as yellow pigment); ColourLex, "Lead White"; present-day EU restriction REACH Regulation (EC) No 1907/2006, Annex XVII, entries 16 and 17
- France, "constat de risque d'exposition au plomb" (1 mg/cm²), Arrêté of 19 August 2011; US definition "lead-based paint" 40 CFR 745.103 (0.5 percent by mass or 1.0 mg/cm²)
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