What research says about air, green space and health

Three studies explore different environmental health questions

Recent research has examined three questions: whether air pollution is linked with tuberculosis, whether nearby green space is linked with dementia in older adults, and how climate affects mosquito-borne diseases. The studies use different methods and cannot be combined into one measure of environmental health risk.

The first study reviewed and combined results from earlier research. The second followed older adults over time. The third reviewed evidence about climate, mosquitoes and disease. A useful point applies to all three: one study rarely settles a question. A finding can be important while still needing confirmation. And when two things are linked, that alone does not show that one caused the other.

Household solid-fuel use was linked with higher tuberculosis incidence

Researchers wanted to understand how household and outdoor air pollution relate to tuberculosis and to estimate the burden linked with fine-particle air pollution. Fine particulate matter, also called PM2.5, consists of very small airborne particles.

The team reviewed 140 studies published through August 2024 and combined their results. Household solid-fuel use was associated with 1.82 times the tuberculosis incidence of the comparison group—about 82% higher. The supplied summary says the researchers also estimated tuberculosis burden linked with PM2.5, but it does not give that estimate or all of the review’s findings ¹.

This review brings together earlier research, but an association does not prove that household fuel use caused tuberculosis. The summary provided here is incomplete, so readers cannot assess all of the results or uncertainties. The findings may help inform research and policy discussions about air quality and tuberculosis, but they do not predict one person’s risk.

More greenery near home was linked with less dementia

Researchers asked whether green space near home was linked with new dementia diagnoses among older adults. They followed 2,993 people in Stockholm who did not have dementia at the start of the study. Over as long as 16 years, 477 developed clinically diagnosed dementia. The researchers measured vegetation around participants’ homes and considered other exposures, including air pollution and traffic noise ².

More greenery within 100 metres of home was associated with a lower rate of dementia during follow-up. The reported hazard ratio was 0.79 for a study-defined increase in greenery. In everyday terms, that is about a 21% lower hazard in the analysis. The association was weaker when researchers measured larger areas around the home. It was stronger among women; the estimate for men was uncertain because its confidence interval included no difference ².

Following people over time helps researchers examine how exposures and health outcomes relate, but it cannot establish that greenery caused the difference. The study took place in a generally affluent urban area of Stockholm, so its findings may not apply to other populations or places. It raises a question about how neighbourhood greenery relates to brain health; it does not show that green space prevents dementia.

Climate can shape mosquito disease, but local patterns differ

The review examined why climate change may affect malaria and dengue differently, even though mosquitoes spread both diseases. Temperature, rainfall and humidity can influence mosquito populations and disease transmission. The authors also considered other factors, including land use, urbanisation, movement of people, immunity, disease-control efforts and the quality of health care ³.

The review describes climate change as creating more favourable conditions for mosquito-borne transmission in many regions, but the effects vary by location and season. It contrasts rapid growth in dengue with a longer-term decline in malaria. It does not give one climate effect that applies everywhere ³.

This is a review of evidence, not an experiment or a forecast of an individual’s risk. It cannot show that climate change caused a particular infection. Its value is in explaining why climate is one part of disease risk, alongside local environments and public health responses.

The studies point to possible links, not simple predictions

Together, the studies show why researchers are examining air pollution, green space and climate as parts of public health. They do not show that any one environmental factor determines a person’s health. The studies look at different questions, use different methods and have different limits. The summary supplied for the air-pollution review also omits important results.

Some questions remain open. It is not clear from these findings how well the results apply to other places and populations, or how much the reported links reflect cause and effect. The climate review also describes several influences on disease patterns, rather than offering a simple forecast. These studies add evidence to ongoing research; they do not provide a personal diagnosis or a precise prediction.