Scientists from Melbourne, Australia have found evidence that ambient air pollution affects the fitness of insect species around the globe, according to a new study in Nature Communications.
By studying houseflies, researchers found that even brief exposure to particulate matter pollution would compromise the olfactory perception of the flies, through accumulation of matter on the sensory receptors of their antennae. The study showed consistent evidence that perception of both reproductive odor and food odors was affected by particulate matter exposure.
Terrestrial insects are declining around the world, both in number and diversity. This study further confirms the hypothesized effects of human-caused pollution on insect populations, including the effects of air pollution in particular.
"While we know that particulate matter exposure can affect the health of organisms, including insects, our research shows that it also reduces insects' crucial ability to detect odours for finding food and mates," said study co-author Professor Mark Elgar.
"This could result in declining populations, including after bushfires and in habitats far from the pollution source.”
The research team published their findings after conducting several related experiments.
First, they collected wild houseflies from the urban area of Beijing, China, and used scanning electron microscopy (SEM) to examine the accumulation of particulate matter (PM) on their antennae. They found that PM accumulation on their antennae increased with the levels of ambient air pollution recorded at the place and time of the flies’ collection.
Next, they exposed lab houseflies for 12 hours to ambient air pollution (100 < AQI ≤ 150) on par with that experienced by wild specimens collected from low to moderate levels of pollution. Upon examination, they discovered that PM was more densely accumulated on the antennae of the houseflies than on their head, thorax, legs and abdomen. They subsequently subjected these flies to a Y-maze to determine their ability to detect and follow food odors and reproductive odors. They found that while uncontaminated control flies tended to correctly enter the arm of the maze with the desired odor, the contaminated houseflies appeared to be selecting the arms of the Y-maze at random.
They also used electroantennography (EAG) assays to examine the specimens’ antennae, confirming that the contamination appeared to reduce the strength of electrical signals sent to the flies’ brains as a result of odors.
"When their antennae become clogged with pollution particles, insects struggle to smell food, a mate, or a place to lay their eggs, and it follows that their populations will decline," Professor Elgar said.
The researchers found that bees, wasps, moths, and flies in bushfire-affected rural areas in Victoria, Australia had PM pollutants on their antennae, even when far from the location of the fire. Professor Elgar noted that even remote and comparatively pristine habitats may have strong concentrations of air pollution “because particulate material can be carried thousands of kilometres by air currents.”