It is well known that air pollution can have severe effects on heart health. In particular, any particles smaller than 2.5 microns — 20 times thinner than a single strand of hair — have the ability to enter the bloodstream through the lungs, increasing the risk of heart attack and stroke.
A new study has revealed how a lesser known form of pollution can accelerate the aging of cardiovascular tissue. This type of air pollution, known as bioaerosol, contains microscopic organisms, such as bacteria, viruses, fungal spores, and pollen, as well as small particles, and is commonly found in garbage stations that collect household waste.
“Urban garbage collection stations are essential in daily life; their enclosed environments and large amounts of kitchen waste promote the growth of microorganisms, posing significant health risks to residents,” said Caiwen Ou from Southern Medical University in China.
“This study demonstrates that high concentrations of pathogenic bioaerosols exist in household garbage collection station environments. Additionally, chronic exposure to these high concentrations can accelerate vascular aging in mice.”
The study, published in Advanced Science, is the first to show that the microbes found in bioaerosols can accelerate the aging of blood vessels, compounding the already known health risks caused by air pollution.
Ou and colleagues also identified how this happens at a molecular level, a discovery that could pave the way to developing treatments against the long-term effects of this type of pollution. They hope that their research will be a wakeup call for governments and regulatory agencies to start implementing stricter policies aimed at protecting people who are chronically exposed to bioaerosols, such as specialized workers and neighbors who live close to garbage collection stations, from these health hazards.
Investigating bioaerosols
To learn more about the effects of bioaerosols on human health, the scientists first looked at historical data from over 8,000 people 45 years or older who took part in a study looking at the overall health of Chinese citizens all over the country.
The participants were divided into four groups based on the levels of exposure of their households to air pollution and bioaerosols. Those in the group with the highest exposure to this type of pollution (96 μg/m3 on average) had a 35% higher risk of reporting strokes, heart attacks, and heart failure after two years compared to the people with the lowest levels of exposure (36 μg/m3 on average).
In order to correct for any outside factors, the scientists adjusted the data according to criteria such as age, gender, smoking status, and established disease, among others. Even after this, they found a statistically significant correlation between exposure to bioaerosols and cardiovascular events.
The researchers then analyzed samples of bioaerosols from a household garbage transfer station in Guangzhou, China. They found that the concentration of bioaerosols in household garbage stations was significantly higher than that of stations located in office buildings and schools, and identified numerous types of bacteria present in the sample.
“The analysis of the samples indicated that a majority of the bioaerosol particles found in garbage stations were small enough to be inhaled,” explained Ou. “Their transmission potential is extensive.”
While these preliminary results were concerning, the researchers still need to establish a causative link between the elevated levels of bioaerosols and a higher risk of strokes and heart attacks. To further investigate this link, they looked at the effects that pathogens found in bioaerosols can have in our health.
Aging blood vessels
The researchers selected a strain of Staphylococcus caprae from the garbage station samples to further investigate its effects on cardiovascular health. This bacterium can naturally be found on our skin, where it is usually harmless, but it is also known to cause severe infections when it manages to make its way into the bloodstream.
When exposing the cells that make up our blood vessels, called endothelial cells, to bioaerosols containing this bacterium, they showed signs of accelerated aging compared to healthy cells. This effect was stronger at higher concentrations of S. caprae, however, the experiments did not include an exact comparison of the concentrations typically found in bioaerosols.
The researchers identified a specific protein that was activated in the presence of the bioaerosols, called NK-κB. This small protein is involved in controlling the immune system to protect the body against external threats, however, when activated in excess, it is linked to inflammation, autoimmune disease, and cancer.
In human cells and in mice, the scientists found that bioaerosols activated this protein, triggering inflammation, which in turn activated genes linked to aging — this was determined by measuring the output of genes known to play a role in cellular aging. In addition, mice exposed to bioaerosols developed thicker and less elastic arteries, which are common signs of vascular aging.
This discovery not only highlights the additional precautions needed when dealing with bioaerosols, but also that the more we know about them, the better situated we are to develop medicines and preventative therapies against the harmful effects of bioaerosols.
“Developing vaccines or immunotherapies targeting specific biological aerosol components may be able to prevent or mitigate their adverse effects on human health,” said Ou. “However, the development and application of these treatment measures require further scientific research and clinical trials to verify safety and effectiveness.”
Next, the scientists aim to conduct further research into how bioaerosols cause inflammation and vascular aging at the molecular level, as well as study how people of different gender, age, and health status respond to bioaerosols to identify potential protective measures.
“We believe that this research can remind governments and regulatory agencies to strengthen monitoring and control of bioaerosols in the air, especially in areas with severe (…) pollution,” said Ou. These may involve stricter emission standards, further health monitoring and additional protective measures for workers in high-risk environments.
“Our objective is to translate our findings into effective public health policies and interventions that reduce the impact of bioaerosols on community health,” Ou concluded.
Reference: Guoxia Zhang, Feiran Zhou, Caiwen Ou, et al., Chronic Exposure to Bioaerosols in PM2.5 from Garbage Stations Accelerates Vascular Aging via the NF-κB/NLRP3 Pathway, Advanced Science (2024). DOI: 10.1002/advs.202404142