Air pollutants disrupt flower scents used by pollinators, review finds

University of Reading-led research reported on 8 October 2026 finds that ozone and nitrogen oxides can make flower scents harder for bees, moths and other pollinators to follow. The review draws on 22 experimental studies and examines what happens when the pollutants occur together. That matters for insects seeking flowers, but the researchers caution that relatively few experiments tested combined exposure.

How ozone and nitrogen oxides affect flower scents

Flowers release scents that help pollinators locate them. According to the review’s indexed abstract, ozone and nitrogen oxides, or NOx, alter the composition and concentration of those scents. The University of Reading’s account says both pollutants make flowers harder for insects to find. The review addresses pollinator performance in experiments; its figures should not be read as measured losses in pollinator populations or crop production.

The Reading account reports an average 42% reduction in pollinator performance under elevated ozone and a 46% reduction under NOx. It gives a 68% average reduction when both pollutants were present. Those are results reported across the studies assessed, not a prediction that every pollinator or location will experience the same decline. The account says only a few studies tested both pollutants together, so the combined-exposure figure has a narrower evidence base.

Why the combined effect is difficult to estimate

The review’s indexed abstract describes the joint effect in its supporting meta-analysis as sub-additive. In the Reading account, the researchers explain that ozone and NOx react with one another in the air, partly offsetting the additional harm that might be expected from adding their separate effects. The account says the extra harm observed in the few combined-exposure studies was smaller than the headline averages might suggest. The 68% figure therefore needs to be read alongside that qualification, rather than as a simple sum of the two individual results.

What an earlier field experiment found

An earlier controlled experiment provides field context for pollutant interactions, although it asked a different question. In 2022, researchers at a University of Reading wheat-field facility exposed predominantly ground-dwelling invertebrate communities to diesel exhaust, ozone, both or control air over two summer seasons. They collected 27,071 specimens from 125 taxonomic groups. Pollutant treatment was associated with differences in community composition; herbivores and pollinators generally responded negatively in diesel-polluted treatments, while some other groups responded positively.

In that experiment, the combined ozone and diesel-exhaust treatment had lower pollutant levels than diesel exhaust alone, likely because the gases reacted. It also had a lesser negative effect on invertebrate abundance and taxonomic richness. The study supports the relevance of pollutant interactions outside a scent-tracking experiment. Its wheat-field, ground-invertebrate results do not establish pollinator population trends across ecosystems or demonstrate the new review’s projected future outcomes.

What the review projects, and what remains uncertain

Under the middle-of-the-road SSP2-4.5 emissions scenario, the review projects that ground-level ozone will rise until around mid-century and decline after 2050 as cleaner energy reduces emissions of ozone precursors. The authors say any rate of pollinator recovery would depend on the emissions pathway and how effectively policies cut emissions. These are scenario-based projections, not observations of future pollution levels or a forecast of measured pollinator population recovery.

The Reading account says most of the evidence examined comes from Europe. It identifies a gap in understanding risks in more heavily polluted regions, including parts of Asia. Together with the small number of combined-exposure studies, that limits how widely the reported averages can be applied. The published account establishes a concern about insects’ ability to find flowers in polluted air; it does not establish the scale of resulting effects on pollinator populations or harvests.