Environment

1. Environmentwell supported · human dataAdded 4 October 2026

   City air pollution spikes track with spikes in daily deaths

   Across 109 daily time-series studies worldwide, short-term rises in air pollution were associated with about 2.0% excess all-cause deaths per typical increment in PM10 particles, with larger effects on respiratory deaths for most pollutants.

   ⚠What it shows: Strong for a link but still city-level pattern watching: results pooled from 109 studies that track daily death counts against daily pollution, which shows association rather than proof of cause for any one person. The effects shrank, though mostly persisted, when several pollutants were modelled at once.Meta-analysis · J Air Waste Manag Assoc

   Full breakdown →All-cause mortality explained →Meta-analysis of time-series studies of air pollution and mortality: effects of gases and particles and the influence of cause of death, age, and season. J Air Waste Manag Assoc 2002
2. Environmentwell supported · human dataAdded 30 September 2026

   Fine particle pollution linked to earlier death even at low levels

   A pooled analysis of 53 cohort studies found that long-term exposure to fine particulate air pollution (PM2.5) is associated with increased risk of premature death, with significant effects seen even below 10 µg/m3. Studies with poorer exposure measurement produced smaller effect estimates, suggesting the true harm may be underestimated.

   ⚠What it shows: About as robust as pollution evidence gets: 53 studies of large populations followed over time, spanning North America, Europe and Asia. It still cannot prove cause and effect on its own, and the finding that cruder pollution measurement produced smaller estimates hints the real risk may be larger than reported.Meta-analysis · Environ Res

   Full breakdown →All-cause mortality explained →The concentration-response between long-term PM(2.5) exposure and mortality; A meta-regression approach. Environ Res 2018
3. Environmentwell supported · human dataAdded 29 September 2026

   Dirtier air days bring more deaths, and weather cannot explain it away

   Across more than a dozen city studies, each 100 micrograms per cubic metre rise in airborne particle concentration was associated with a 6% increase in daily deaths. The link held across warm and cold climates and survived detailed adjustment for weather, leading the author to judge a causal association the most reasonable interpretation.

   ⚠What it shows: A remarkably consistent signal pooled from more than a dozen city studies, though all of them tracked populations rather than testing anything, so cause cannot be proven outright; the author argues the sameness of the effect across climates makes a causal link the most reasonable reading. It also dates from 1994, when particle levels and measurement methods differed from today's.Meta-analysis · Environ Res

   Full breakdown →All-cause mortality explained →Air pollution and daily mortality: a review and meta analysis. Environ Res 1994
4. Environmentpreliminary · human dataAdded 18 September 2026

   No clear link between fine air pollution and ovarian cancer, pooled data show

   A pooled analysis found no association between fine particulate air pollution (PM2.5) and ovarian cancer, and only a weak elevation in endometrial cancer risk. Across 145 studies, research on environmental chemicals and these cancers remains sparse.

   ⚠What it shows: Reassuring but thin: the ovarian result pools just four studies and the endometrial one five, so the picture could shift as more research lands. The authors themselves call the wider literature on these cancers sparse.Review · Environ Res

   Full breakdown →Epidemiologic research on environmental chemical exposures and ovarian and endometrial cancers: a systematic review. Environ Res 2026
5. Environmentpreliminary · human dataAdded 7 September 2026

   A hot workout jolts your immune signalling for hours

   Pooling 36 studies of 498 nonacclimatised people exercising at 26°C or hotter, a single session immediately raised both pro- and anti-inflammatory blood markers, with IL-6 still elevated two hours later and higher peak core temperature amplifying some of the responses.

   ⚠What it shows: Consistent but noisy: results pooled from 36 studies covering 498 people who were not acclimatised to heat, 86% of them men. The studies disagreed with each other enough that the authors themselves call predictions from their model possibly unreliable.Study · Temperature (Austin)

   Full breakdown →Sauna Therapy →Acute exertional heat stress alters both pro- and anti-inflammatory blood markers: A meta-analysis. Temperature (Austin) 2026
6. Environmentwell supported · human dataAdded 5 September 2026

   City air is quietly shaving millilitres off healthy lungs

   Pooled results from 23 studies link outdoor particulate air pollution with lower lung function in healthy adults: each 10 µg/m3 rise in short-term PM2.5 exposure was associated with a 7.02 mL drop in FEV1, and a 10 µg/m3 difference in long-term PM10 exposure with a 71.36 mL lower FEV1 overall.

   ⚠What it shows: Solid enough to take seriously: results pooled from 23 studies of healthy adults all point the same way. The studies followed people rather than testing on them, though, and for long-term exposure smoking and other habits could explain part of the effect.Meta-analysis · Occup Environ Med

   Full breakdown →Effect of outdoor particulate air pollution on FEV(1) in healthy adults: a systematic review and meta-analysis. Occup Environ Med 2019
7. Environmentwell supported · human dataAdded 1 September 2026

   Every extra 10 µg/m³ of particle pollution tracked with 15.1% more heart deaths

   In a review pooling 145 studies from China, every 10 µg/m³ of long-term PM2.5 exposure was associated with 15.1% higher cardiovascular mortality and 21.0% higher lung cancer mortality, with short-term pollution spikes also linked to more deaths and illness.

   ⚠What it shows: Strong and consistent, but built from following populations rather than testing exposures on anyone, so pollution cannot be proven to be the direct cause. The 145 pooled studies all come from China, where other risks of city living travel with dirty air and are hard to fully separate.Meta-analysis · J Environ Sci (China)

   Full breakdown →Fine particulate matter and cardiorespiratory health in China: A systematic review and meta-analysis of epidemiological studies. J Environ Sci (China) 2023
8. Environmentwell supported · human dataAdded 30 August 2026

   Heat training sped up time trials but left VO2max untouched

   Pooled results from 11 randomised trials in athletes (215 participants, mean age 26.09 years, 91% men) found heat acclimation improved time-trial performance and lowered maximal heart rate by 7 beats per minute, but produced no significant change in VO2max, exercise heart rate, core temperature, mean skin temperature, plasma volume or blood lactate. Changes in thermal comfort and perceived exertion were judged too small to be meaningful.

   ⚠What it shows: Reasonable evidence but thin on the ground: results pooled from 11 trials with 215 athletes between them, and 91% of those athletes were men, so it says little about women. The performance gain was modest and most of the physiological markers people expect heat training to shift did not budge.Meta-analysis · J Sports Sci Med

   Full breakdown →VO₂max explained →VO2max Calculator →Physiological Responses to Heat Acclimation: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Sports Sci Med 2019
9. Environmentpreliminary · human dataAdded 27 August 2026

   Dirty air and blood clots: the link may be real but it is small and shaky

   Pooling 19 studies of more than 4.5 million people found no significant overall association between long-term PM2.5 or PM10 exposure and venous blood clots; a modest PM2.5 association emerged only in sensitivity analyses limited to studies reporting exposure the same way.

   ⚠What it shows: Treat this as unsettled: the underlying studies followed people rather than testing anything on them, and while 19 studies of over 4.5 million people mostly showed no clear link, a modest association appeared only when analysts kept to studies that measured exposure the same way. The studies also disagreed with each other heavily, which is why the authors stop short of a firm conclusion.Study · Thromb Haemost

   Full breakdown →Ambient Particulate Matter Exposure and Risk of Venous Thromboembolism: An Updated Systematic Review and Meta-Analysis. Thromb Haemost 2026
10. Environmentwell supported · human dataAdded 25 August 2026

    Most of secondhand smoke's estimated deaths were in non-smokers

    Researchers estimate that in Spain in 2020, 747 deaths from lung cancer and ischaemic heart disease were attributable to secondhand smoke, rising to 2242 deaths when chronic obstructive pulmonary disease and cerebrovascular disease were included. Of the attributable deaths, 60.9% occurred in non-smokers and 75.1% in men.

    ⚠What it shows: These are statistical estimates, not counted deaths: researchers combined national exposure surveys with risks pooled from earlier studies, so the totals depend on those inputs being right. The underlying link between secondhand smoke, lung cancer and heart disease is long established.Meta-analysis · Arch Bronconeumol

    Full breakdown →All-cause mortality explained →Healthy Lifestyle & Life Expectancy →Mortality Attributable to Environmental Tobacco Smoke Exposure in Spain in 2020. Arch Bronconeumol 2023
11. Environmentpreliminary · human dataAdded 23 August 2026

    The air you breathe may be tied to how your brain ages

    A sweep of the research found that people with higher historical air pollution exposure tended to score worse on tests of cognitive function, though the two studies tracking decline over time disagreed with each other.

    ⚠What it shows: Suggestive at best: a sweep of all the studies on this found only eight worth including, most relying on indirect estimates of pollution exposure and unclear cognitive testing. It can show that pollution and worse scores travel together, not that one causes the other.Systematic review · Age Ageing

    Full breakdown →Is air pollution associated with increased risk of cognitive decline? A systematic review. Age Ageing 2015
12. Environmentpreliminary · human dataAdded 22 August 2026

    Dry heat, not humid heat, carried the bigger death toll

    In data from 353 locations across China, hot dry days were linked with a 10.18% excess rate of non-accidental deaths, compared with 3.21% for hot humid days, and high heat combined with low humidity raised risk by more than the sum of each alone.

    ⚠What it shows: Strong signal, not proof: researchers tracked death records and weather across 353 locations in China rather than testing anything, so other differences between places and days could shape the pattern. Whether the same holds in climates outside China is unknown.Meta-analysis · Environ Int

    Full breakdown →All-cause mortality explained →The joint and interaction effect of high temperature and humidity on mortality in China. Environ Int 2023
13. Environmentpreliminary · human dataAdded 21 August 2026

    Stroke deaths climb on the hottest days, and women and the elderly are hit hardest

    On the hottest days in 12 Chinese cities, stroke death risk was 1.63 times higher for ischaemic stroke and 1.36 times higher for haemorrhagic stroke than on typical warm days. Women, older people and those with less education were hit hardest.

    ⚠What it shows: A clear pattern rather than proof: researchers compared death records with temperatures across 12 cities, following what happened rather than testing anything, so other hot-day factors could play a part. The link held after accounting for air pollution, humidity and season.Meta-analysis · Sci Total Environ

    Full breakdown →Heat and mortality for ischemic and hemorrhagic stroke in 12 cities of Jiangsu Province, China. Sci Total Environ 2017
14. Environmentwell supported · human dataAdded 16 August 2026

    Living near traffic is linked to earlier death and adult-onset asthma

    Long-term exposure to traffic-related air pollution is associated with higher all-cause, circulatory, ischaemic heart disease and lung cancer mortality, as well as asthma onset in children and adults, with high or moderate-to-high confidence across 353 studies.

    ⚠What it shows: A strong and carefully vetted signal: an independent expert panel reviewed 353 studies and rated confidence high or moderate-to-high for these links. Almost all the research followed people rather than testing anything, so it shows association, not proof of cause.Meta-analysis · Environ Int

    Full breakdown →All-cause mortality explained →Long-term exposure to traffic-related air pollution and selected health outcomes: A systematic review and meta-analysis. Environ Int 2022
15. Environmentwell supported · human dataAdded 8 August 2026

    Cold waves carry a 40% higher death risk for people with diabetes

    Pooled data from eight studies link cold-wave exposure to a 40% increase in diabetes-related mortality risk (relative risk 1.40); the rise in diabetes-related illness was smaller and not statistically significant.

    ⚠What it shows: Meta-analysis of eight observational studies; the morbidity estimate was not statistically significant (its confidence interval crossed 1) and risk varied across studies, suggesting environmental and healthcare disparities between settings.Meta-analysis · Front Public Health

    Full breakdown →Impact of cold waves on diabetes-related morbidity and mortality: a meta-analysis. Front Public Health 2025
16. Environmentpreliminary · human dataAdded 6 August 2026

    Summer ozone tracks with heart-death risk

    In a meta-analysis of cohort studies, every 10 µg/m3 increase in long-term ozone exposure was associated with modestly higher cardiovascular mortality (RR 1.0105) and cardiovascular morbidity (RR 1.0578). The mortality association was clearer for warm-season ozone (RR 1.0186) than for annual average exposure (RR 0.9971), and estimates were higher in females (RR 1.1135) than males (RR 1.0707).

    ⚠What it shows: Meta-analysis of observational cohort studies, so it shows association and not causation; the authors describe the long-term ozone evidence as sparse, the male and Asia-region estimates had confidence intervals crossing no effect, and most data came from Europe and the USA.Review · China CDC Wkly

    Full breakdown →Investigation of the Association between Long-term Ozone Exposure and Cardiovascular Disease: A Meta-Analysis Addressing Exposure Windows, Vulnerable Populations, and Spatial Variation. China CDC Wkly 2026
17. Environmentpreliminary · human dataAdded 6 August 2026

    Living near lead-releasing sites tied to weaker memory

    Living closer to a lead-releasing facility was associated with poorer episodic memory two years later in two cohorts of older adults (n = 1638 and n = 741): every 5 km closer corresponded to episodic memory scores 0.05 standard deviations lower.

    ⚠What it shows: Observational data from two cohorts of older adults; proximity to a facility is a stand-in for actual lead exposure, which was not directly measured. Association, not causation, and residual confounding is possible despite adjustment.Meta-analysis · Alzheimers Dement

    Full breakdown →Association between proximity to a lead-releasing facility and cognition in diverse cohorts. Alzheimers Dement 2026
18. Environmentwell supported · human dataAdded 6 August 2026

    Particle pollution and death: likely cause, not chance

    A critical appraisal of 15 published reviews concluded that the short-term association between airborne particles and cardiopulmonary mortality is valid and satisfies most standard criteria for causality, with effects observed even where air quality standards were respected.

    ⚠What it shows: A 2001 critical assessment of the arguments in 15 existing reviews of ecological time-series studies, not a pooled analysis of individual data; time-series designs compare days rather than people, and the exposure landscape has changed since publication.Meta-analysis · J Air Waste Manag Assoc

    Full breakdown →All-cause mortality explained →Healthy Lifestyle & Life Expectancy →Air pollution and health: correlation or causality? The case of the relationship between exposure to particles and cardiopulmonary mortality. J Air Waste Manag Assoc 2001
19. Environmentpreliminary · human dataAdded 6 August 2026

    Beijing's cleaner air came with a smaller daily death toll

    Across five periods in Beijing between 1990 and 2017, concentrations of SO2, NO2, PM10 and PM2.5 fell by up to 42%, 10%, 33% and 15%, and the estimated short-term mortality effect of each pollutant shrank alongside them: PM2.5's effect on cardiovascular and respiratory deaths falling by up to 0.33% and 0.13%.

    ⚠What it shows: Longitudinal comparative study in one city: published effect estimates for 1990-2013 pooled by random-effects meta-analysis and combined with newly analysed 2015-2017 daily data. The design is ecological, so parallel changes in healthcare, smoking or population structure cannot be excluded.Meta-analysis · Chemosphere

    Full breakdown →All-cause mortality explained →Healthy Lifestyle & Life Expectancy →The impacts of continuous improvements in air quality on mortality in Beijing: A longitudinal comparative study. Chemosphere 2022
20. Environmentwell supported · human dataAdded 6 August 2026

    Long-term PM2.5 linked to worse Covid outcomes

    In a meta-analysis of cohort studies with individual-level data, each 1 µg/m3 increase in long-term PM2.5 exposure was associated with a 4% higher risk of SARS-CoV-2 infection, an 11% higher risk of COVID-19 hospitalisation and a 9% higher risk of COVID-19 death; NO2 was associated with hospitalisation and death, while ozone showed no association with any outcome.

    ⚠What it shows: Systematic review and random-effects meta-analysis restricted to cohort studies with individual-level data, pooled only where more than three studies existed per exposure-outcome pair. Observational throughout, so residual confounding remains possible, and country of study explained much of the heterogeneity between results.Meta-analysis · Environ Pollut

    Full breakdown →Investigating links between long-term air pollution exposure and the risk of SARS-CoV-2 infection, COVID-19 hospitalisation and mortality: a systematic review and meta-analysis of cohort studies. Environ Pollut 2025
21. Environmentpreliminary · human dataAdded 6 August 2026

    Cold snaps raise stroke deaths days after they hit

    Across 12 counties in Hubei, China, covering 42 739 stroke deaths between 2009 and 2012, cold spells were associated with a pooled stroke mortality risk of 1.180 at lags of 3-14 days, with the effect appearing after a delay of 2-3 days and lasting about 10 days, while heatwaves carried a pooled risk of 1.114 concentrated in the first 0-2 days.

    ⚠What it shows: Observational multivariate meta-analysis pooling daily mortality and weather records from 12 counties in one Chinese province over four years; ecological time-series design with no individual data, and county-level estimates varied widely, from 0.968 to 1.523 for cold spells.Meta-analysis · Zhonghua Liu Xing Bing Xue Za Zhi

    Full breakdown →All-cause mortality explained →[Impact of daily mean temperature, cold spells, and heat waves on stroke mortality a multivariable Meta-analysis from 12 counties of Hubei province, China]. Zhonghua Liu Xing Bing Xue Za Zhi 2017
22. Environmentwell supported · human dataAdded 6 August 2026

    Extreme cold outranks heat as the deadlier extreme

    Pooling 58 observational studies, extreme cold carried the highest all-cause mortality risk at a relative risk of 1.478, above heatwaves at 1.280 and extreme heat at 1.145; heatwaves were also associated with more hospitalisations (1.060) and emergency department visits (1.047).

    ⚠What it shows: Systematic review and meta-analysis of 58 observational studies published between 2000 and 2024, so all estimates are associations from population records rather than controlled comparisons; definitions of extreme cold, extreme heat and heatwave vary between studies, and few studies covered length of stay or costs.Meta-analysis · Int J Hyg Environ Health

    Full breakdown →All-cause mortality explained →A systematic review and meta-analysis comparing the health burden of extreme heat and cold on mortality and urgent care utilization. Int J Hyg Environ Health 2026
23. Environmentwell supported · human dataAdded 6 August 2026

    Heat plus high ozone: mortality risks stack up

    In a meta-analysis of 28 studies, days combining heat with high ozone were associated with a 17% higher overall mortality risk than days without co-exposure, with elevated cardiovascular and respiratory mortality and increased risks across age and gender groups and in urban areas.

    ⚠What it shows: Systematic review of 78 studies with 28 pooled by random-effects meta-analysis; all observational, with the authors flagging risk of bias from inadequate confounder adjustment and unclear handling of missing data, plus inconsistent definitions of what counts as a compound heat-ozone event.Meta-analysis · Environ Pollut

    Full breakdown →All-cause mortality explained →Effect of compound heat and ozone events on health outcomes: a systematic review and meta-analysis of epidemiological evidence. Environ Pollut 2026

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