Generated Summary
The Lancet Pathfinder Commission conducted an umbrella review of relevant systematic reviews to assess the evidence on the near-term health effects of greenhouse gas mitigation, including both modelling studies and evaluated implemented actions. The Commission’s aim was to assess the potential and achieved magnitude of the benefits for health and climate of different mitigation actions and, where possible, the factors facilitating or impeding implementation. The umbrella review was conducted across multiple peer-reviewed literature databases, identifying 6902 records, of which 317 full texts were screened. From the full text screening, 26 reviews presented quantitative estimates of both changes in greenhouse gas emissions and health outcomes. 200 mitigation actions were identified across all sectors, of which 178 (89%) presented modelled estimates of the effects of climate mitigation actions on greenhouse gas emissions and health across different sectors and scales. The Commission also searched peer-reviewed and grey literature to further identify examples of implemented actions that had measured and reported both emission reductions and health co-impacts. These examples provide evidence on the realities of implementing mitigation actions in different geographical locations and socioeconomic settings, and at a variety of spatial scales.
Key Findings & Statistics
- Major benefits to health are delivered through reductions in air pollution, consumption of healthy sustainable diets, and the promotion of active travel and public transport.
- Clean cookstoves had the greatest estimated median health co-benefit (a reduction of 1279 YLL per 100000 population per year, based on data from India), followed by dietary changes (306 YLL per 100000 population per year).
- Actions in the transportation sector resulted in a median reduction of 60 YLL per 100000 population per year.
- In the electricity generation sector, we estimated a median reduction of 11 YLL per 100000 population per year, with some evidence for larger benefits in India (a reduction of 149 YLL per 100000 population per year for the single reported study).
- Multisectoral actions might achieve very high mitigation intensity, but their effects were highly variable, depending on the country context.
- Although global modelling studies show potential large benefits to health from reductions in ambient air pollution, these are not currently reflected in the data within systematic reviews.
- Major additional benefits would result from reduced household air pollution, largely in low-income countries.
- The Global Methane Assessment shows that CH4 emissions from human activities can be reduced by up to 45% this decade, thus avoiding almost 0.3°C of global warming by 2045.
- A 45% reduction would prevent an estimated 260000 premature deaths from tropospheric O3, 775000 asthma-related hospital visits, 73 billion hours of lost labour from extreme heat, and 25 megatonnes (million tonnes) of crop losses annually.
- The EAT-Lancet Commission estimated that about 10-11 million premature deaths from non-communicable diseases could be prevented annually worldwide by 2040 if the so-called planetary health diet was widely consumed.
- Physical inactivity is a major risk factor for non-communicable diseases and has been estimated to be responsible for about 5 million premature deaths worldwide annually.
- Modelled evidence from the umbrella review shows that some actions might deliver large benefits for health with only small benefits for climate mitigation and vice versa, whereas some actions have the potential to deliver significant wins for the environment and health.
- The greatest average mitigation intensities were seen for electricity generation, followed by multisectoral actions.
- Actions to improve cookstoves had the highest median health co-impact intensity with a reduction of 1279 YLL per 100000 population per year, followed by actions to change diets with a median intensity reduction of 306 YLL per 100000 population per year.
- The greatest estimated health co-impact intensities were seen in the AFOLU sector via the diet pathway, which was found to have average reductions in YLL in excess of 300 (ie, 300 years of life gained) per 100000 people per year.
- Actions in the transport sector had the largest number of actions with quantified estimates of the relationship between mitigation action and health (n=217), with pathways to health that were spread across air pollution, physical activity, and injuries (figure 4).
- The study showed that the home upgrade on average reduced gas use by 2.326 gigajoules and electricity use by 81.9 kilowatt-hours over the 3-month winter period, which can be converted to a reduction of 0.128 tonnes of CO₂eq per upgrade for gas and 0.078 tonnes of CO₂eq for electricity.
- The programme resulted in an estimated reduction of 1149 tonnes of CO2 emissions between 2011 and 2013, and 34.5 DALYs and two deaths were avoided over the same period.
Other Important Findings
- Health co-benefits are additional to the benefits gained from reducing the impacts of climate change on health.
- Many actions to mitigate greenhouse gas emissions can also deliver near-term health co-benefits, for example from reduced air pollution, consumption of healthy diets, and increased physical activity.
- The Commission’s aim is to assess the potential and achieved magnitude of the benefits for health and climate of different mitigation actions and, where possible, the factors facilitating or impeding implementation.
- Actions that cut across multiple sectors had the second largest average mitigation intensity after electricity generation.
- The replacement of fossil fuel-powered private cars with electric cars powered by electricity from renewables will reduce greenhouse gas emissions and air pollution from NO₂ and probably also from PM2.5, but it does not achieve health benefits from increased physical activity, nor will it reduce road danger for pedestrians and cyclists.
- The greatest average mitigation intensities were seen for electricity generation, followed by multisectoral actions.
- The replacement of fossil fuel-powered private cars with electric cars powered by electricity from renewables will reduce greenhouse gas emissions and air pollution from NO₂ and probably also from PM2.5, but it does not achieve health benefits from increased physical activity, nor will it reduce road danger for pedestrians and cyclists.
Limitations Noted in the Document
- Although global modelling studies show potential large benefits to health from reductions in ambient air pollution, these are not currently reflected in the data within systematic reviews which tend to feature small-scale actions with limited benefits.
- Although human health is among the most well evidenced co-benefits of mitigation actions, uncertainties exist about the magnitude of these mitigation actions in different contexts and how to implement such actions at scale.
- Although the report acknowledges but does not focus on the health effects of climate change.
- Modelled evidence from the umbrella review shows that some actions might deliver large benefits for health with only small benefits for climate mitigation and vice versa, whereas some actions have the potential to deliver significant wins for the environment and health.
- The magnitude of the benefits depends not only on the intensity of their effects but also on the extent to which they are implemented at scale.
- Within the umbrella review, actions affecting health via ambient air pollution used a wide range of ERFs to estimate health impacts. This heterogeneity was often compounded by opaque methods that did not detail the exact functions used, making quantitative inferences regarding the impact different ERFs had on effect sizes difficult.
- As seen in electricity generation with actions impacting health via air pollution, this same study found the greatest reductions in YLL in India (-149 YLL per 100000 population per year).
- Variation in estimates is also dependent on the exposure-response function (ERF) used, the health outcomes included, the counterfactual used for comparison (for non-linear functions), the magnitude of the mitigation action, and other factors.
Conclusion
The Lancet Pathfinder Commission’s report highlights the critical need for deep, rapid cuts in greenhouse gas emissions to limit global temperature increases and reduce future risks from climate change. The research emphasizes the inadequacy of current progress and stresses the importance of actions that not only mitigate emissions but also deliver near-term health co-benefits. The study’s methodology involved an umbrella review of systematic reviews, identifying 200 mitigation actions across various sectors. The findings underscore the potential for significant wins for the environment and health, with actions in the energy, AFOLU, and transport sectors showing the greatest potential. The analysis emphasizes the importance of considering the full range of pathways by which actions can achieve significant mitigation and health benefits, advocating for systems approaches that integrate adaptation and mitigation. These approaches must address underlying structures driving inequity and rising greenhouse gas emissions. A key takeaway is that health co-benefits are not merely ancillary but can be a powerful incentive for more ambitious climate action. The study emphasizes the need to quantify the health and greenhouse gas effects of implemented mitigation actions. There is a need for more applied research focused on mechanisms to achieve large-scale changes. The study’s recommendations include a call for leadership, integration of health into climate policies, and better evidence for decision-making. The creation of a coalition of actors is proposed to accelerate progress towards net-zero emissions and improve health. The commission advocates for the development of systems approaches that incorporate health into climate mitigation policies. This approach implies going beyond health as a co-benefit, and beyond the design of ex-post compensatory measures to mitigate inequalities.