Assessment of Lead Contamination in Drinking Water from Lead Solder Plumbing in Old Buildings in Zaria, Kaduna State

This study assesses lead contamination in drinking water supplied through plumbing systems using lead-based solder joints in older residential and institutional buildings in Zaria, Kaduna State, North West Nigeria. Lead solder was widely used in plumbing installations before the mid-1990s and continues to serve older buildings in Nigerian cities, raising the risk of lead leaching into drinking water particularly after stagnation. Water samples were collected from first-draw and flushed taps in forty buildings constructed before 1995 in Zaria's government residential area and old township, sampling both early morning first-draw water after at least six hours of stagnation and water after two minutes of flushing to distinguish fixed plumbing contribution from supply line contribution. Lead concentrations were measured by inductively coupled plasma mass spectrometry. Plumbing inspection documented the proportion of lead-soldered joints in sampled buildings. Results show that first-draw lead concentrations exceed the WHO guideline of 0.01 milligrams per litre in 28 of 40 buildings, with maximum values reaching 0.087 milligrams per litre in buildings with the highest proportion of lead-soldered joints and soft acidic water supply. Flushed samples show substantially lower concentrations, confirming local plumbing as the dominant source. Children's exposure risk is calculated to be above the provisional tolerable weekly intake in the majority of non-flushed samples. The study recommends a building-level plumbing replacement programme starting with schools and creches in Zaria. Keywords: lead contamination, drinking water, lead solder, plumbing, Zaria.