Background: Air pollution containing nickel (Ni) compounds from metal industry, combustion, or natural events (e.g., forest fires), may affect the risk of respiratory cancer in residents in surrounding areas. In Norway, the counties of Agder and Finnmark are the most relevant regions where emissions and ambient levels of Ni experienced by the general population are assumed relatively high due to nearby metal smelters or refineries. However, no ecological analysis has been conducted to assess the possible impact on incidence rates of respiratory cancer from airborne Ni exposure on the population-level.
Objectives: This study aims to investigate temporal and spatial patterns of atmospheric Ni concentrations, including both high and low levels, and the association with respiratory cancer rates across 357 Norwegian municipalities (2024 administrative structure).
Methods: Ni concentrations in moss samples (Hylocomium splendens) collected at 3,579 sites all over mainland Norway (1977, 1985, 1990, 1995, 2000, 2005, 2010 and 2015) were obtained from a database at the Norwegian Institute for Air Research and used to derive municipality-level exposure metrics: mean Ni concentration (µg g?¹) and cumulative Ni concentration (µg g?¹ × years). We obtained sex?specific case counts and age?standardized incidence rates (Norway 2014 standard) for lung and sinonasal cancer from the Cancer Registry of Norway, aggregated by municipality and by 10?year periods from 1975 to 2024. We will model the bivariate spatial relationship between the Ni metrics and subsequent age-standardized rates using Lee’s L statistic (integrating Pearsons’s r and Moran’s I) to identify municipalities with significant Ni-cancer associations. We will also adjust for smoking prevalence at the county level by regressing sex-specific, age-standardized lung cancer rates on smoking prevalence and use the deviance residuals as smoking-adjusted rates in the Lee’s L statistic. Standardized incidence ratios (SIRs) for a cohort of Norwegian metal refinery workers (n=~6000, employed 1910–2015) compared with the general population, will inform excess cases likely attributable to occupational exposure, which in turn may be subtracted from the corresponding municipality rates. Further, a negative control outcome approach will address potential residual confounding.
Results: A preliminary assessment of the geospatial biomonitoring data of atmospheric Ni, showed consistently high concentrations in municipalities in both Agder and Finnmark for the time periods 1977, 1985 and 1990. Also, age-standardized rates of respiratory cancer were higher (than the national average) for the two counties, following time periods with high activity in nearby nickel smelters or refineries. Further, estimated observed geographic variation in bivariate associations between Ni concentrations and respiratory cancer rates, at municipality-level, will be presented and illustrated in maps, separate for males and for females. Patterns of high Ni concentration and high respiratory cancer rates, as well as low-high, high-low, and low-low, patterns of association, for single or clustered municipalities, will be interpreted.
Conclusion/Implications: This study will provide new insights into the potential role of airborne Ni compounds across mainland Norway, as environmental determinants of lung and sinonasal cancer. The results may be important for preventive purposes, for control of environmental pollution, and for regulatory bodies informing public health internationally.