A national assessment of reticulation-level exposure risk indicators in drinking-water infrastructure in Aotearoa New Zealand

Background

Drinking water reticulation networks are a critical yet understudied component of public health infrastructure. Despite recognition of microbial and chemical risks from ageing distribution systems, few studies have quantified these exposures or assessed associated population health burden nationally.

Objective

To assess public health risks from New Zealand’s drinking water reticulation networks and identify demographic disparities.

Methods

We conducted a nationwide exposure risk assessment using spatial data on 57,000 km of municipal drinking water pipes across 629 Water Distribution Zones, covering 88% of the population. We developed key exposure metrics to assess enteric disease risk (proportion of pipes in poor/very poor condition), potential lead leaching (presence of metal pipes), and possible asbestos exposure (presence of asbestos cement pipes). Exposure was categorised into population-weighted tertiles to assess inequities by ethnicity and area-level deprivation.

Results

About 30.7% of New Zealand’s pipes were in poor or very poor condition. Metal and asbestos cement pipes comprised 12.4% and 19.8% of the network, respectively, of which72.2% and 96.5% were in poor or very poor condition. Māori, Pacific Peoples, and those in high-deprivation areas were disproportionately exposed to the worst pipe conditions and asbestos pipes.

Significance

New Zealand’s ageing drinking water infrastructure may pose microbial and chemical risks, with inequitable impacts across demographic groups. Our findings underscore the need for targeted infrastructure investment and regulatory reform to ensure safe, equitable access to drinking water.