Respiratory syncytial virus (RSV) is the primary cause of acute lower respiratory infections in children, bronchiolitis in particular. Airborne particulate matter (PM) may influence the children's immune system and foster the spread of RSV infection.

We aimed to verify whether PM10 exposure is associated with hospitalization due to RSV bronchiolitis.

We selected hospital discharge records (HRD) with ICD-9-CM code 466.11 of infants < 1 year of age, occurring in the epidemic seasons of two years (2012–2013) in Lombardy, Italy. Cases were assigned daily PM10 and apparent temperature levels of the capital city of their residential province. Different exposure windows were considered: single days preceding hospitalization (lag 0 to 30), their average estimates (lag 0–1 to 0–30), and the four weeks preceding hospitalization (week 1 to 4). Negative binomial regression models adjusted for apparent temperature and season were applied to the daily counts of hospitalizations in each province. Results were expressed as incidence rate ratios (IRR) and 95% confidence intervals (95%CI) per 10 µg/m³ increase in PM10 concentration. Random effects meta-analyses of province-specific IRR were performed to obtain regional estimates.

2814 HRD met our inclusion criteria; males represented about 55% of the cases. A 6% increased risk of hospitalization (95%CI: 1.03–1.10) was found at lag 0 and an almost overlapping 7% increase at lag 1. IRR ranged from 1.03 to 1.05 between lags 2 and 11. No increased risk was observed from lag 12. When considering averaged daily lags, risk estimates gradually increased in the two weeks preceding hospitalization from 1.08 (1.04–1.12) at lag 0–1 to 1.15 (1.08–1.23) between lags 0–11 and 0–13. Analyses on weekly lags showed a risk increase of 6% (1.01–1.12) during week 1 and of 7% (1.02–1.13) during week 2.

Our study found a clear association between short- and medium-term PM10 exposures and increased risk of hospitalization due to RSV bronchiolitis among infants.

呼吸道合胞病毒（RSV）是儿童（尤其是细支气管炎）急性下呼吸道感染的主要原因。空气中的颗粒物（PM）可能会影响儿童的免疫系统并促进RSV感染的传播。

我们旨在验证PM10暴露是否与RSV细支气管炎引起的住院相关。

我们选择了在意大利伦巴第的两年（2012-2013年）流行季节发生的，ICD-9-CM代码为466.11的1岁以下婴儿的医院出院记录（HRD）。每天为病例分配其居住省会省会城市的PM10和表观温度水平。考虑了不同的暴露时间窗：住院前几天（滞后0到30），其平均估计值（滞后0-1到0-30）和住院前四个星期（第1-4周）。调整了表观温度和季节的负二项式回归模型应用于每个省的住院日计数。结果以每10 µg / m ^3的发生率比（IRR）和95％置信区间（95％CI）表示增加PM10浓度。进行了针对各省的内部收益率的随机效应荟萃分析，以获得区域估计值。

2814 HRD符合我们的纳入标准；男性约占病例的55％。滞后0发现住院风险增加了6％（95％CI：1.03-1.10），滞后1增加了几乎重叠的7％。IRR在滞后2和滞后11之间的范围为1.03至1.05。滞后12.当考虑平均每日滞后时，在住院前两周，风险估计从滞后0–1的1.08（1.04–1.12）逐渐增加到滞后0–11和0–13之间的1.15（1.08–1.23）。对每周滞后的分析显示，第1周的风险增加了6％（1.01-1.12），第2周的风险增加了7％（1.02-1.13）。

我们的研究发现，在婴儿的RSV细支气管炎引起的PM10短期和中期暴露与住院风险增加之间存在明显的关联。