Exposure to ambient fine particulate matter with an aerodynamic diameter <2.5 μg·m^–3 (PM_2.5) is a risk factor for pulmonary and systemic autoimmune diseases; however, evidence on which PM_2.5 chemical components are more harmful is still scant. Our goal is to investigate potential associations between major PM_2.5 components and interstitial lung disease (ILD) onset in rheumatoid arthritis (RA).

New-onset RA subjects identified from a US healthcare insurance database (MarketScan) were followed for new onset of RA-associated ILD (RA-ILD) from 2011 to 2018. Annual concentrations of ambient PM_2.5 chemical components (i.e. sulfate, nitrate, ammonium, organic matter, black carbon, mineral dust and sea salt) were estimated by combining satellite retrievals with chemical transport modelling and refined by geographically weighted regression. Exposures from 2006 up to 1 year before ILD onset or end of study were assigned to subjects based on their core-based statistical area or metropolitan division codes. A novel time-to-event quantile-based g (generalised)-computation approach was used to estimate potential associations between RA-ILD onset and the exposure mixture of all seven PM_2.5 chemical components adjusting for age, sex and prior chronic obstructive pulmonary disease (as a proxy for smoking).

We followed 280 516 new-onset RA patients and detected 2194 RA-ILD cases across 1 394 385 person-years. The adjusted hazard ratio for RA-ILD onset was 1.54 (95% CI 1.47–1.63) per every decile increase in all seven exposures. Ammonium, mineral dust and black carbon contributed more to ILD risk than the other PM_2.5 components.

Exposure to components of PM_2.5, particularly ammonium, increases ILD risk in RA.

暴露于空气动力学直径 <2.5 μg·m ^–3 (PM _2.5 ) 的环境细颗粒物是肺部和全身性自身免疫性疾病的危险因素；然而，关于 PM _2.5化学成分更有害的证据仍然很少。我们的目标是调查主要 PM _2.5成分与类风湿性关节炎 (RA) 间质性肺病 (ILD) 发病之间的潜在关联。

从美国医疗保险数据库 (MarketScan) 确定的新发 RA 受试者从 2011 年到 2018 年跟踪新发 RA 相关 ILD (RA-ILD)。环境 PM _2.5化学成分（即硫酸盐、硝酸盐、铵盐）的年浓度、有机物、黑碳、矿物尘埃和海盐）通过将卫星反演与化学传输模型相结合进行估计，并通过地理加权回归进行改进。从 2006 年到 ILD 发病或研究结束前 1 年的暴露被分配给基于核心统计区域或大都市分区代码的受试者。一种新的基于事件分位数的 g（广义）计算方法用于估计 RA-ILD 发病与所有 7 PM 的暴露混合物之间的潜在关联_2.5根据年龄、性别和既往慢性阻塞性肺病（作为吸烟的代表）调整的化学成分。

我们跟踪了 280516 名新发 RA 患者，在 1394385 人年中发现了 2194 例 RA-ILD 病例。在所有七次暴露中，每增加十分位数，RA-ILD 发作的调整风险比为 1.54 (95% CI 1.47–1.63)。_{与其他 PM 2.5}成分相比，铵、矿物粉尘和黑碳对 ILD 风险的贡献更大。

暴露于 PM _2.5的成分，尤其是铵，会增加 RA 中 ILD 的风险。