Objectives

This study aimed to determine the effect of ambient air pollution and temperature on stillbirth in Tehran.

Methods

In this time-series study, the effect of O₃ (ppb), CO (ppm), NO₂ (ppb), SO₂ (ppb), PM_2.5 (μg/m³), and minimum, maximum, and mean daily temperature (°C) on stillbirth was evaluated in Tehran, Iran between March 2015 and March 2018. Using a quasi-Poisson regression model in combination with a Distributed Lag Non-linear Models (DLNM), the Relative Risk (RR) was estimated through comparing the high temperature (99th, 95th, and 75th percentiles) and low temperature (1st, 5th, and 25th percentiles) with the median. The effect of air pollution was estimated for each 1-, 5-, or 10-unit increase in the concentration during lags (days) 0–21.

Results

Among air pollutants, only a 5-ppm increase in the SO₂ concentration in lag 0 increased the risk of stillbirth significantly (RR = 1.062; 1.002–1.125). The largest effect of heat was observed while comparing the 99th percentile of minimum daily temperature (26.9 °C) with the median temperature (13.2 °C), which was not statistically significant (RR = 1.25; 0.95–1.65). As for cold, a non-significant protective effect was observed while comparing the 1st percentile of maximum daily temperature (3.1 °C) with the median temperature (23.2 °C) (RR = 0.92; 0.72–1.19).

Conclusion

Each 5-ppm increase in the mean daily SO₂ in lag 0 increased the risk of stillbirth by 6% while other air pollutants had no significant effects on stillbirth. In lags 0 and 1, the heat increased the risk of stillbirth while the cold had protective effects, which were not statistically significant.

中文翻译：

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环境空气污染和温度对死产风险的影响：分布式滞后非线性时间序列分析

 目标

这项研究旨在确定德黑兰环境空气污染和温度对死产的影响。

 方法

在此时间序列研究中，O ₃ (ppb)、CO (ppm)、NO ₂ (ppb)、SO ₂ (ppb)、PM _2.5 (μg/m ³ ) 以及每日最小值、最大值和平均值的影响2015 年 3 月至 2018 年 3 月期间，对伊朗德黑兰的死产温度 (°C) 进行了评估。使用准泊松回归模型结合分布式滞后非线性模型 (DLNM)，通过以下方式估计相对风险 (RR)：将高温（第 99、95 和 75 个百分位数）和低温（第 1、5 和 25 个百分位数）与中值进行比较。在滞后（天）0-21 期间，浓度每增加 1、5 或 10 个单位，就会估计空气污染的影响。

 结果

在空气污染物中，滞后 0 期间 SO ₂浓度仅增加 5 ppm 就会显着增加死产风险（RR = 1.062；1.002–1.125）。在将每日最低气温 (26.9 °C) 的第 99 个百分位与中值温度 (13.2 °C) 进行比较时，观察到热量的最大影响，但没有统计学意义 (RR = 1.25; 0.95–1.65)。至于寒冷，在比较每日最高温度的第一个百分位（3.1°C）与平均温度（23.2°C）时，观察到不显着的保护作用（RR = 0.92；0.72-1.19）。

 结论

滞后 0 中日均 SO ₂每增加 5 ppm，死产风险就会增加 6%，而其他空气污染物对死产没有显着影响。在滞后 0 和 1 中，高温会增加死产的风险，而寒冷则具有保护作用，但没有统计学意义。