This report assesses winter air quality monitoring undertaken in Carterton between 2010 and 2025, focusing on particulate matter (PM10 and PM2.5), to inform future monitoring if new Environmental Limits for Air Quality are set. Results indicate that Carterton is likely to meet the national daily PM10 standard but regularly exceeds World Health Organization guideline levels for PM2.5 during winter. Carterton’s winter air quality is closely comparable to Masterton, despite its smaller population, reflecting similar home‑heating practices and meteorological conditions that limit pollutant dispersion. 

Long‑term trend analysis is constrained by changes in monitoring methods and monitoring frequency; however, benchmarking against Masterton suggests a gradual reduction in home‑heating emissions over time. 

Mitchell T. 2026. Carterton winter air quality 2010 to 2025. Greater Wellington Regional Council, Publication No. GW/KI-T-25-33 Wellington.