随着全球气温升高，全世界许多地区面临发生更大规模或更频繁的野火的风险。野火不仅威胁当地居民的健康，其产生的烟雾还会扩散到较大的范围。一个国际合作团队近日发表的两项研究显示，在全球 749 个城市中，每年有超过 3.35 万人的死亡可直接归因于野火来源 PM2.5 污染；仅仅在巴西，每年就有超过 48 000 人因野火空气污染入院。
图片来源：Pixabay
编译 武大可
编辑 戚译引
野火不但可能对人体造成直接伤害，其产生的有毒物质也会随空气扩散，在较大的时间和空间尺度上影响人类健康。澳大利亚莫纳什大学（Monash University）公共卫生和预防医学学院的郭玉明教授、李珊珊教授、叶婷婷博士，中山大学公共卫生学院陈功博副教授和国际合作者组成的研究团队对全球范围的野火污染与每日死亡人数的关系进行了研究，建立了暴露于空气中野火相关的细颗粒物（PM2.5）短期暴露与全因、呼吸系统和心血管疾病死亡之间的综合联系。该团队还对巴西的野火来源 PM2.5 污染与医院入院的关系进行了专门研究。这两项研究 9 月 8 日在线发表在国际权威期刊《柳叶刀-星球健康》（Lancet Planetary Health）上。
近年来，野火造成了广泛的破坏，例如澳大利亚 2019-2020 年火灾季节，烧毁 4500 万英亩（约 18 万平方公里）；2019 年初以来，美国加利福尼亚州烧毁 120 万英亩（约 4860 平方公里）；还有西伯利亚的 190 处野火，其释放的大量二氧化碳创下了新纪录，总计已超过世界上所有其他地区野火的总和。
郭玉明表示，野火本身就对健康有直接的影响，包括造成伤害和损害心理健康，“而且其污染还能扩散超过 1000 公里。随着气候变化的加剧，野火带来的风险还将增加。
PM2.5 微粒是野火烟尘中最令人担忧的污染物之一，具有这一直径的颗粒能够穿过肺泡进入循环。作者在论文中指出，由于野火 PM2.5 的化学组成、较小尺寸和与之关联的高温条件，其毒性可能超过了城市来源的 PM2.5。
在第一项研究中，作者收集了 2000 年 1 月 1 日至 2016 年 12 月 31 日期间 43 个国家和地区的 749 个城市中超过 6560 万例因死因别死亡数据，并与同期野火来源 PM2.5 的日均浓度相对应。研究发现在全球 749 个城市中，每年有超过3.35万人的死亡可直接归因于野火来源 PM2.5 污染。数据显示，可归因于野火来源 PM2.5 污染死亡人数较多的国家包括：日本（47 个城市每年归因死亡人数超过 7 千），墨西哥（10 个城市每年归因死亡人数超过 3 千），中国（15 个城市每年归因死亡人数超过 1 千），泰国（62 个城市每年归因死亡人数超过 5 千）和美国（210 个城市每年归因死亡人数超过 3 千）。
大部分的死亡数据来自多城市多国合作研究 [Multi-City Multi-Country (MCC) Collaborative Study]。PM2.5 的每日浓度由机器学习、化学传输模型、地面监测空气污染和气象数据综合估算得出。
研究团队总结：“政策制定者和公共卫生专业工作者应当提高对野火污染的意识，引导公众对野火作出及时响应，并采取措施减少暴露。有效的荒地管理政策和操作也应得到落实，以尽可能管理植被覆盖和缓解气候变化。”
第二项研究则关注巴西的野火来源空气污染，包括亚马孙雨林巴西境内部分。自 20 世纪 90 年代以来，由于采矿、伐木和农业等人类活动造成的森林砍伐和退化，巴西各地的火灾不断增加。火灾通常发生在 8 月至 11 月的旱季，而先前的研究显示旱季的持续时间正在延长。虽然大多数野火发生在巴西偏远地区，但郭玉明说：“亚马孙地区野火产生的有毒烟尘可以上升到 2000 至 2500 公里的高空，并传播很远的距离，威胁到数千英里以外的人们。”
这项研究调查了 2000 年初到 2015 年底，巴西的 1814 个城市超过 1.43 亿人的住院情况，覆盖了巴西近 80% 的人口，并将这些数据与每日城市来源 PM2.5 水平进行了比较。这是目前巴西最大、最全面的野火健康影响研究，揭示了野火来源 PM2.5 对健康的危害，确定了野火来源 PM2.5 的短期暴露与呼吸系统疾病、心血管疾病和全因住院率之间的关联。
研究发现，每年有 48 000 多名巴西人因野火空气污染入院，相当于每 10 万居民中有 35 人。这些病例主要集中在巴西北部、南部和中西部地区的城市，东北部地区的发病率最低。研究还发现，总计住院率“在 4 岁或以下的儿童、5 至 9 岁的儿童以及 80 岁及以上人群中尤其高”。
2020 年，巴西的野火数量增加了 12.7%，达到十年来的最高水平。亚马孙雨林地区发生了 260 起重大火灾，过火面积超过 1050 平方公里——大约相当于洛杉矶的面积。尽管自 2004 年起，巴西政府采取多种措施减缓森林砍伐和禁止未经授权的户外用火，但仍有超过 75% 的火灾发生在亚马孙地区。
郭玉明说：“这项研究非常及时，揭示了野火烟雾中的悬浮颗粒物的健康威胁，因为近年来，巴西以及世界各地的火灾引起了全球的广泛关注，而我们这在之前就注意到了。”
论文信息
【标题】Mortality risk attributable to wildfire-related PM2.5 pollution: a global time series study in 749 locations
【作者】Gongbo Chen, Yuming Guo, Xu Yue, Shilu Tong, Antonio Gasparrini, Michelle L Bell, Ben Armstrong, Joel Schwartz, Jouni J K Jaakkola, Antonella Zanobetti, Eric Lavigne, Paulo Hilario Nascimento Saldiva, Haidong Kan, Dominic Royé, Ai Milojevic, Ala Overcenco, Aleš Urban, Alexandra Schneider, Alireza Entezari, Ana Maria Vicedo-Cabrera, Ariana Zeka, Aurelio Tobias, Baltazar Nunes, Barrak Alahmad, Bertil Forsberg, Shih-Chun Pan, Carmen Íñiguez, Caroline Ameling, César De la Cruz Valencia, Christofer Åström, Danny Houthuijs, Do Van Dung, Evangelia Samoli, Fatemeh Mayvaneh, Francesco Sera, Gabriel Carrasco-Escobar, Yadong Lei, Hans Orru, Ho Kim, Iulian-Horia Holobaca, Jan Kyselý, João Paulo Teixeira, Joana Madureira, Klea Katsouyanni, Magali Hurtado-Díaz, Marek Maasikmets, Martina S Ragettli, Masahiro Hashizume, Massimo Stafoggia, Mathilde Pascal, Matteo Scortichini, Micheline de Sousa Zanotti Stagliorio Coêlho, Nicolás Valdés Ortega, Niilo R I Ryti, Noah Scovronick, Patricia Matus, Patrick Goodman, Rebecca M Garland, Rosana Abrutzky, Samuel Osorio Garcia, Shilpa Rao, Simona Fratianni, Tran Ngoc Dang, Valentina Colistro, Veronika Huber, Whanhee Lee, Xerxes Seposo, Yasushi Honda, Yue Leon Guo, Tingting Ye, Wenhua Yu, Michael J Abramson, Jonathan M Samet, Shanshan Li
【期刊】Lancet Planetary Health
【时间】September 2021
【DOI】https://doi.org/10.1016/S2542-5196(21)00200-X
【链接】
https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(21)00200-X/fulltext
【摘要】
Background Many regions of the world are now facing more frequent and unprecedentedly large wildfires. However, the association between wildfire-related PM2.5 and mortality has not been well characterised. We aimed to comprehensively assess the association between short-term exposure to wildfire-related PM2.5 and mortality across various regions of the world.
Methods For this time series study, data on daily counts of deaths for all causes, cardiovascular causes, and respiratory causes were collected from 749 cities in 43 countries and regions during 2000–16. Daily concentrations of wildfire- related PM2.5 were estimated using the three-dimensional chemical transport model GEOS-Chem at a 0·25° × 0·25° resolution. The association between wildfire-related PM2.5 exposure and mortality was examined using a quasi-Poisson time series model in each city considering both the current-day and lag effects, and the effect estimates were then pooled using a random-effects meta-analysis. Based on these pooled effect estimates, the population attributable fraction and relative risk (RR) of annual mortality due to acute wildfire-related PM2.5 exposure was calculated.
Findings 65.6 million all-cause deaths, 15.1 million cardiovascular deaths, and 6.8 million respiratory deaths were included in our analyses. The pooled RRs of mortality associated with each 10 μg/m3 increase in the 3-day moving average (lag 0–2 days) of wildfire-related PM2.5 exposure were 1.019 (95% CI 1.016-1.022) for all-cause mortality, 1.017 (1.012–1.021) for cardiovascular mortality, and 1.019 (1.013–1.025) for respiratory mortality. Overall, 0.62% (95% CI 0.48–0.75) of all-cause deaths, 0.55% (0.43–0.67) of cardiovascular deaths, and 0.64% (0.50–0.78) of respiratory deaths were annually attributable to the acute impacts of wildfire-related PM2.5 exposure during the study period.
Interpretation Short-term exposure to wildfire-related PM2.5 was associated with increased risk of mortality. Urgent action is needed to reduce health risks from the increasing wildfires.
论文信息
【标题】Risk and burden of hospital admissions associated with wildfire-related PM2.5 in Brazil, 2000–15: a nationwide time-series study
【作者】Tingting Ye, Yuming Guo, Gongbo Chen, Xu Yue, Rongbin Xu, Micheline de Sousa Zanotti Stagliorio Coêlho, Paulo Hilario Nascimento Saldiva, Qi Zhao, Shanshan Li
【期刊】Lancet Planetary Health
【日期】September 2021
【DOI】https://doi.org/10.1016/S2542-5196(21)00173-X
【链接】
http://www.thelancet.com/journals/lanplh/article/S2542-5196(21)00173-X
【摘要】Background In the context of climate change and deforestation, Brazil is facing more frequent and unprecedented wildfires. Wildfire-related PM2.5 is associated with multiple adverse health outcomes; however, the magnitude of these associations in the Brazilian context is unclear. We aimed to estimate the association between daily exposure to wildfire-related PM2.5 and cause-specific hospital admission and attributable health burden in the Brazilian population using a nationwide dataset from 2000 to 2015.
Methods In this nationwide time-series analysis, data for daily all-cause, cardiovascular, and respiratory hospital admissions were collected through the Brazilian Unified Health System from 1814 municipalities in Brazil between Jan 1, 2000, and Dec 31, 2015. Daily concentrations of wildfire-related PM2.5 were estimated using the 3D chemical transport model GEOS-Chem at a 2.0° latitude by 2.5° longitude resolution. A time-series analysis was fitted using quasi-Poisson regression to quantify municipality-specific effect estimates, which were then pooled at the regional and national levels using random-effects meta-analyses. Analyses were stratified by sex and ten age groups. The attributable fraction and attributable cases of hospital admissions due to wildfire-related PM2.5 were also calculated.
Findings At the national level, a 10 μg/m3 increase in wildfire-related PM2.5 was associated with a 1.65% (95% CI 1.51–1.80) increase in all-cause hospital admissions, a 5.09% (4.73–5.44) increase in respiratory hospital admissions, and a 1.10% (0.78–1.42) increase in cardiovascular hospital admissions, over 0–1 days after the exposure. The effect estimates for all-cause hospital admission did not vary by sex, but were particularly high in children aged 4 years or younger (4.88% [95% CI 4·47–5·28]), children aged 5–9 years (2.33% [1.77–2.90]), and people aged 80 years and older (3.70% [3.20–4.20]) compared with other age groups. We estimated that 0.53% (95% CI 0.48–0.58) of all-cause hospital admissions were attributable to wildfire-related PM2.5, corresponding to 35 cases (95% CI 32–38) per 100 000 residents annually. The attributable rate was greatest for municipalities in the north, south, and central-west regions, and lowest in the northeast region. Results were consistent for all-cause and respiratory diseases across regions, but remained inconsistent for cardiovascular diseases.
Interpretation Short-term exposure to wildfire-related PM2.5 was associated with increased risks of all-cause, respiratory, and cardiovascular hospital admissions, particularly among children (0–9 years) and older people (≥80 years). Greater attention should be paid to reducing exposure to wildfire smoke, particularly for the most susceptible populations.
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