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Human activities, urbanization, and industrialization contribute to pollution that affects climate and air quality. A main atmospheric pollutant, the tropospheric ozone (O 3 ), can damage living organisms by generating oxidative radicals, causing respiratory problems in humans and reducing yields and growth in plants. Exposure to high concentrations of O 3 can result in oxidative stress in plants and animals, eventually leading to substantial ecological consequences. Plants produce volatile organic compounds (VOCs) emitted in the environment and detected by pollinators (mainly by their antennae), foraging for nutritious resources. Several pollinators, including honey bees, recognize and discriminate flowers through olfactory cues and memory. Exposure to different concentrations of O 3 was shown to alter the emission of floral VOCs by plants as well as their lifetime in the atmosphere, potentially impacting plant-pollinator interactions. In this report, we assessed the impacts of exposure to field-realistic concentrations of O 3 on honey bees' antennal response to floral VOCs, on their olfactory recall and discriminative capacity and on their antioxidant responses. Antennal activity is altered depending on VOCs structure and O 3 concentrations. During the behavioral tests, we first check consistency between olfactory learning rates and memory scores after 15 min. Then bees exposed to 120 and 200 ppb of ozone do not exert specific recall responses with rewarded VOCs 90 min after learning, compared to controls whose specific recall responses were consistent between time points. We also report for the first time in honey bees how the superoxide dismutase enzyme, an antioxidant defense against oxidative stress, saw its enzymatic activity rate decreases after exposure to 80 ppb of ozone. This work tends to demonstrate how hurtful can be the impact of air pollutants upon pollinators themselves and how this type of pollution needs to be addressed in future studies aiming at characterizing plant-insect interactions more accurately., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Air pollution stemming from human activities affects the environment in which plant and animal species live and interact. Similar to primary air pollutants which are emitted, secondary air pollutants, such as tropospheric ozone (O 3 ) formed from nitrogen oxides, are also harmful to human health and plant physiology. Yet, few reports studied the effects of O 3 on pollinators' physiology, despite that this pollutant, with its high oxidative potential, likely affects pollinators behaviors, especially the perception of signals they rely on to navigate their environment. Volatile Organic Compounds (VOCs) released by plants are used as signals by different animals. For pollination services, VOCs attract different insects to the flowers and strengthen these interactions. Here, we used the honey bee Apis mellifera as a model to characterize the effects of acute exposure to different realistic mixing ratios of O 3 (80-, 120-, and 200-ppb) on two crucial aspects: first, how exposed honey bees detect VOCs; and second, how O 3 affects these pollinators' learning and memory processes. With electroantennogram (EAG) recordings, we showed that increasing O 3 mixing ratios had a biphasic effect: an initial 25% decrease of the antennal activity when bees were tested directly after exposure (O 3 direct effect), followed by a 25% increase in activity and response when bees were allowed a two-hour rest after exposure (O 3 delayed effect). In parallel, during olfactory conditioning, increasing O 3 mixing ratios in both exposure protocols scarcely affected olfactory learning, followed by a decrease in recall of learned odors and an increase of response to new odors, leading to a higher generalization rate (i.e., discrimination impairment). These results suggest a link between O 3 -related oxidative stress and olfactory coding disturbance in the honey bee brain. If ozone affects the pollinators' olfaction, foraging behaviors may be modified, in addition with a possible long-term harmful effect on pollination services., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)