Before 1945, exterior house paint contained up to 50 % lead by weight. While lead levels diminished thereafter, lead-based house paints were not banned until 1965. Metal primers were lead-based until the 1990s. A pre-war house can carry more than 80 kg of lead in exterior paint. Health authorities have estimated more than 250,000 houses are, or have been, painted with lead.
The Ministry of Health and Master Painters New Zealand have produced some great guidance on managing and removing lead-based paint. However, if paint has been removed without following that guidance, soils close to the house can be more than 1 % lead by weight, many times greater than the national Soil Contaminant Standard. Children who happen to swallow soil or indoor dust can suffer subtle neurotoxic effects; at higher levels of exposure, children and pets may experience a range of acute poisoning symptoms. Back in 1986, the Dunedin Longitudinal Study tested more than 500 11-year-olds for elevated blood lead, finding 10 cases of significant exposure. Nine of these ten were apparently associated with renovations in the home in the months before testing.
HAIL Environmental has a particular interest in assessing and managing lead in soil: last year Dr. Dave Bull chaired and organised two sessions on lead contamination at the Australasian Land and Groundwater Association's 2018 New Zealand conference in Christchurch - for full details see the ALGA website. The Waste Management Institute New Zealand (WasteMINZ) has set up a Residential Lead Group in response, and Dave is a founding member of that group. Property owners or regulators needing advice on lead contamination can call Dave on 021 036 7764, or contact their local HAIL specialist.