The story so far: Tiny, invisible particles, smaller than 30 times the breadth of human hair, wreak damage to more than 7.5 billion people’s health globally. Now imagine if this microscopic particulate pollution, called PM2.5, were to drive the next global public health threat — antibiotic resistance, when disease-causing bacteria become uniquely immune to drugs. A new analysis published in the Lancet Planetary Journalsuggests a link between the two: for every 10% rise in air pollution, researchers found a correlated increase in antibiotic resistance of 1.1% across countries and continents.
Researchers have, for long, flagged the growing burden of drug-resistant bacteria. Antimicrobial resistance (AMR, when any microbe is resistant to a drug) killed more people globally than malaria or HIV/AIDS, a 2019 survey found; it was directly responsible for 1.27 million deaths and associated with an estimated 4.95 million deaths globally. Dr. Kamini Walia, a senior Indian Council of Medical Research (ICMR) scientist last year warned that antibiotic resistance “has the potential of taking the form of a pandemic in the near future.” This pandemic-in-waiting has been shaped by the injudicious use of antibiotics, poor sanitation facilities, the high burden of disease, and poor public health infrastructure, among other reasons, evidence shows.
(For top health news of the day, subscribe to our newsletter Health Matters)
The present analysis is “the first to show how air pollution affects antibiotic resistance globally” — findings which have “substantial policy and environmental implications by presenting a new pathway to combat clinical antibiotic resistance by controlling environmental pollution”.
How big a threat is antibiotic resistance?
Once upon a time, ciprofloxacin, an antibiotic, was used to treat urinary tract infections usually caused by Escherichia coli (E. coli), also among the most common bacteria type in India. E. coli’s resistance tociprofloxacin now varies from 8.4% to 92.9%, per the World Health Organisation.
Multidrug-resistant strains of TB (MDR-TB) have also rendered the two most potent TB drugs, isoniazid and rifampin, ineffective, with patients now having less than a 60% chance of recovery.
Global deaths attributable to and associated with bacterial antimicrobial resistance by infectious syndrome. Photo Credit: “Global burden of bacterial antimicrobial resistance in 2019: a systematic analysis” (The Lancet, January 2022)
Put simply, changes in bacteria cause the drugs used to treat the infection caused by said bacteria to become less effective. In the absence of the right drug, the patient will never recover from the infection or the disease. Antibiotic resistance adds to the disease burden of a nation, making it harder to treat old enemies such as tuberculosis, cholera, and pneumonia, among other infectious diseases.
It also risks widening healthcare inequities, where patients contend with delayed recovery and extended hospitalisation. “It puts patients undergoing major surgeries and treatments, such as chemotherapy, at a greater risk. Patients often recover from advanced medical procedures but succumb to untreatable infections,” noted Sowmya Swaminathan, former Chief Scientist at WHO.
ALSO READ | How can India deal with the challenge of anti-microbial resistance? An expert speaks
Numerous statistics show India leads the world in antibiotic use. Indiscriminate use of antibiotics among people and animals, poor hygiene and sanitation facilities, and lack of awareness have fueled this rise, experts note. The COVID-19 pandemic only accelerated this trend, as the country witnessed a surge in sales of antibiotics such as azithromycin (used to treat bronchitis and pneumonia).
In addition, the increased circulation of antibiotic-resistant bacteria and antibiotic-resistance genes (ARGs) across channels (such as humans, animals, and environments) further creates new pathways of transmission. A 2019 study found India’s rivers, lakes and other water sources were concentrated with antimicrobial-resistant bacteria and their genes (Ganga and Yamuna reported varying degrees of drug-resistant bacteria). Pharmaceutical wastewater and hospital discards, not treated adequately, were the sources. AMR was a classic “tragedy of the commons,” Dr. V. Ramasubramanian, an infectious diseases consultant, told The Hindu earlier.
What does the study show?
The new analysis focuses on the environmental dissemination of ARGs. With every 1% rise in PM2.5 pollution, antibiotic resistance increased between 0.5-1.9% depending on the pathogen — a link which has only intensified with time. The researchers added that this airborne spread may have also caused premature deaths in India and China, among other countries in South Asia, North Africa and the Middle East which are population dense. An average of 18.2 million years of life was lost in 2018 worldwide, resulting in an annual economic loss of $395 billion (more than Pakistan’s GDP) due to premature deaths.
The gist
The paper is unique in its scale and scope: global antibiotic resistance is driven by multiple factors, one being the “effect derived from the environment, which is poorly understood in relation to antibiotic resistance”. The researchers collected data from 116 countries spanning almost two decades, to observe the link between rising PM2.5 and antibiotic resistance. The researchers also analysed other predictors, including sanitation services, antibiotic use, population, education, climate. The final dataset included nine pathogens— Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, Enterobacter aerogenes or E cloacae, Enterococcus faecalis, and Enterococcus faecium— and 43 types of antibiotic agents.
The researchers recognised air as a “direct pathway and key vector for disseminating antibiotic resistance”. For instance, PM2.5 emissions from burning firewood in homes for cooking or heating could carry bacteria and antibiotic-resistant genes, be transmitted over long distances, and eventually be inhaled by individuals. PM2.5 is known to penetrate the body’s defences, entering the bloodstream and lungs, associated with chronic conditions such as cancer, heart disease and asthma. Worryingly, PM2.5’s contribution to antibiotic resistance was greater than that of antibiotic use or due to drinking water services, the analysis found.
How air pollutants affect antibiotic resistance is “still unclear,” however. As an observational paper, the analysis could not show a cause-and-effect relationship and acknowledged the need for “more medical evidence... to verify this occurrence.” Other limitations include limited datasets provided by countries and overlapping impacts of social, economic, and environmental factors — all of which “should be introduced to comprehensively assess the association with antibiotic resistance”.
How is air linked to antiobiotic resistance?
Antibiotic-resistant bacteria and genes travel through different pathways: food, soil, water, air, and even direct contact with sources such as animals. The hypothesis is that ARGs, when emitted from, say, hospitals or livestock farming, could latch on to pollutant particles, which were found to contain “diverse antibiotic-resistant bacteria and antibiotic-resistance genes, which are transferred between environments and directly inhaled by humans, causing respiratory-tract injury and infection.”
When suspended in the environment or breathed into the lungs, the ARGs could enter the bacteria found in the human body and solidify its resistance to drugs. “PM 2.5 can facilitate the horizontal gene transfer of antibiotic-resistant genes between bacteria,” the research found.
Pathways of antibiotic-resistance dissemination. Photo Credit: “Association between particulate matter (PM)2·5 air pollution and clinical antibiotic resistance: a global analysis” (Lancet Planetary Health, August 2023)
Think of the air, which is laden with unhealthy amounts of PM2.5, as a hyperspace for antibiotic-resistant bacteria and ARGs to travel. More than 7.3 billion people globally — and 93% of India’s population — are exposed to unsafe average annual levels of PM2.5. PM2.5 contains a high concentration of antibiotic resistance-determinant genes, and these are particles can travel far and wide due to wind speed, water evaporation, and dust transport. They can also be replenished from the environment and anthropogenic settings, as the study notes, making the daily intake of ARGs far more than one’s exposure to genes in drinking water. ARGs are also more abundant in urban air particles than in sediment, soil or rivers, the analysis showed.
It added: “The association between PM2·5 and antibiotic resistance is increasing at an accelerating rate, which could hasten the beginning of a so-called post-antibiotic era.”
How can this shape policy around AMR?
Antibiotic resistance is not a novel war — researchers have sounded the alarm well before the COVID-19 pandemic. The present focus on environmental factors, however, illustrates that, in the war against bacteria, addressing air pollution could help plug one hole, while measures to combat other drivers of antibiotic resistance continue. Antibiotic use in itself is expected rapidly increase in low- and middle-income countries like India by 2050. India in 2017 released the National Action Plan to address AMR; yet most States are yet to devise a region-specific framework that addresses hyperlocal factors shaping AMR’s trajectory.
“Antibiotic resistance and air pollution are each in their own right among the greatest threats to global health,” the lead author, Prof. Hong Chen of Zhejiang University in China, said to a media outlet. “Until now, we didn’t have a clear picture of the possible links between the two, but this work suggests the benefits of controlling air pollution could be twofold: not only will it reduce the harmful effects of poor air quality, it could also play a major role in combatting the rise and spread of antibiotic-resistant bacteria.”
China’s case is instructive, the analysis noted. China during the 2010s implemented restrictions on antibiotic sales and adopted a warlike stance on air pollution (the reduced air pollution in seven years equalled what the U.S. did in three decades). The result? A decline in the twin challenges of PM2.5 and antibiotic resistance — a trend researchers predict is likely to endure.
- Tiny, invisible particles, smaller than 30 times the breadth of human hair, wreak damage to more than 7.5 billion people’s health globally. Now imagine if this microscopic particulate pollution, called PM2.5, were to drive the next global public health threat — antibiotic resistance, when disease-causing bacteria become uniquely immune to drugs.
- Numerous statistics show India leads the world in antibiotic use. Indiscriminate use of antibiotics among people and animals, poor hygiene and sanitation facilities, and lack of awareness have fueled this rise, experts note.
- When suspended in the environment or breathed into the lungs, the ARGs could enter the bacteria found in the human body and solidify its resistance to drugs. “PM 2.5 can facilitate the horizontal gene transfer of antibiotic-resistant genes between bacteria,” the research found.
