Microorganisms In Pollution

Microorganisms are found all around the world, from volcanoes to oceans and snow-capped mountains, their presence is widely distributed in the air, land, and water; in a similar way to environmental pollution, because of this, the interaction between microorganisms and pollutants is remarkable throughout history. Previously, I have introduced the word "bioaerosols" which is the biological component of the air that includes pollen, fungi, bacteria, and viruses; bioaerosol consists mainly of microorganisms that are found naturally in water bodies, plant surfaces, rocks, and buildings.

To understand this I want to discuss a little about the concept of "microbiome", the microbiome are natural colonies of microorganisms that are associated with a living organism or geographic location; rivers, fish, dogs, and cats have one, even the human body has a microbiome in the lungs, stomach, skin, blood, and much more. The natural microbiome is not a complication for the health of the host organisms or the environment, they are usually neutral microorganisms, even can help and favor the host with their presence; bioaerosols are very important for the propagation of living organisms in nature since they allow the exchange of genetic material in different habitats. 

The situation becomes different when pathogenic microorganisms are integrated into the colony, the pathogens compete with the natural microbiome; if the pathogen defeats the microbiome and the immune system, infectious microbial diseases occur in the host. Clean air also has a healthy microbiome, this consists of populations of natural microorganisms in the air, these can be seasonal or relatively constant over time; however, air pollution changes these conditions. 

The percentage of polluted air varies according to the country from 2% to 15% of the total air, it is estimated that bioaerosols constitute 5 to 34% of the mixture of air pollutants; this percentage includes viruses, cells or bacterial cells and fungal fragments, as well as fungal spores and protozoa. In image 1 we see a photo was taken in allergy season, people's exposure to airborne biological pollutants increases during this time, which can trigger negative health effects; the main pollutants of the season include pollen, odors, volatile compounds, organic residual parts, among others.

Image 1: The child plays with dandelions in nature during allergy season.

Its sources are diverse, although the microorganisms that contribute to air pollution come from sources such as soil, water, and the decomposition of organic matter; garbage, landfills, sewage treatment plants, composting facilities, and traffic are important sources that allow the growth, development, and spread of microorganisms in the environment. 

These microorganisms can even be transported by air currents and move between distant places, also, insects or raindrops can spread these biological pollutants. Humans contribute to the production of biological aerosols by sneezing, coughing, or by introducing significant amounts of microorganisms into the atmosphere through our activities. 

Generally, people who are sick with microorganisms can infect others through this respiratory route; additionally, other human sources of microorganisms include household activities such as cooking, vacuuming, carpeting, and places like the bedroom, kitchen, bathroom, or work area. Fungal spores constitute between 5 and 20% of the dust in the domestic environment, microorganisms in the air inside residential buildings are mainly concentrated in dust particles; aquariums can also be a potential source of bioaerosols. 

Other sources of bioaerosols include places with high levels of humidity (basements, bathrooms, and vacation homes) can also promote the growth and further spread of microorganisms. Studies show that the presence of carbon monoxide, humidity, and ozone concentrations are the main factors affecting the biodiversity of bacteria and the percentage of pathogenic bacteria present in the outdoor air; this can damage the natural stability of the environment and wreak havoc on plant and animal populations. 

Microorganisms are characterized by mutating very quickly to adapt to their environment, in this case, they can be further stimulated by mutagens from environmental pollution. Mutations can generate new types of microorganisms, this varies according to the species and conditions that occur in the specific geographic locations. 

These DNA mutations ensure that the mutant microorganisms have a greater ability to survive the environment (or deliberately kill/incapacitate the individual cell), if it is functional, the mutation can be shared between the colony and its descendants; although this is not always suitable for other living organisms, since this mutations can also generate new biochemical processes in microorganisms, consequently it can cause diseases in the organisms that surround them, unlike previous processes that did not cause any problem. 

The best-known mutation today would be the case of COVID-19; this virus mutated from an animal, giving it the ability to infect humans, which has happened previously in history. The mutation is an adaptive characteristic of microorganisms, although COVID-19 mutation was not caused by environmental contamination; the mutations caused by external pollutants work similarly. Landfills (Image 2) are an important source of biological contamination, the food waste and other factors allow the growth and development of microorganisms; species tend to adapt to these environments to metabolize substances that surround them such as plastic

Image 2: Landfills are proper places for the formation of bacteria.

Exposure to these microorganisms is not suitable for humans or animals in large quantities, much less for infectious organisms. Scientific research has linked bioaerosols and airborne biological pollutants with the occurrence of adverse health effects, including infectious diseases and allergies, as well as other acute toxic effects and cancers. Airborne pollutants, especially bacteria, fungi, and viruses can cause asthma, fever, bronchitis, chronic lung failure, lung cancer, cardiovascular disease, gastrointestinal tract infections, tuberculosis, allergic reactions, sinusitis, conjunctivitis, and infections ranging from acute to acute. In image 3 we see a diagram of the path that is followed by bioaerosols and pollutant microorganisms. The emission of these microorganisms is originated from the water, soil, the activities of plants and humans; these microorganisms can be pathogenic or not. From there, they are transported through the air and can reach the clouds, later, they are deposited on the land, water, or are absorbed by humans, animals, or plants. The emissions and presence of bioaerosols are associated with the functions of cloud formation and biochemical natural cycles.

Image 3: Diagram of the pathway of bioaerosols in nature.

The microbiological fraction in the air is influenced by the source, volume of emissions, distance, place, survival, dispersion, climatic conditions, among others. Nature is amazing, the adaptability of microorganisms such as bacteria and fungi to contaminated environments has allowed these microorganisms the necessary adaptations for the bioremediation of contaminated places (for example bacteria that clean plastics and petroleum).  On the other hand, microorganisms and pathogens that are found in nature can interact with drug residues in water sources and landfills, this could give them resistance to antibiotics, greatly hindering the treatment of infections; the topic of drug-resistant microorganisms is also trending in medicine due to the high concern it generates. The above implies that the wastewater treatment sites are crucial to avoid the spread of this type of microorganisms, which are of great concern to public health.

According to the OECD (Organization for Economic Cooperation and Development), bioaerosols are responsible for premature deaths, respiratory diseases, economic losses including medical expenses (approximately $ 21 billion worldwide), environmental degradation, and material losses. That is why the emissions of this type of microorganisms must be anticipated and controlled, in addition to carrying out the respective care in nature, cities, countryside, industries, landfills, in addition to our homes to prevent environmental pollution from exceeding natural levels and becoming a dangerous situation for the health of the air, land, and water at a global level. At the same time, it is a priority to avoid the spread of pathogenic and dangerous microorganisms that originated in the human-made processes since they are the main cause of risk to the lives of people, animals, plants, and the environment around the world.

References

• Siebielec, Sylwia & Woźniak, Małgorzata & Gałązka, Anna & Siebielec, Grzegorz. (2020). Microorganisms as indoor and outdoor air biological pollution. 59. 115-127. 10.21307/PM-2020.59.2.009. 

• Moelling K, Broecker F. Air Microbiome and Pollution: Composition and Potential Effects on Human Health, Including SARS Coronavirus Infection. J Environ Public Health. 2020 May 28;2020:1646943. doi: 10.1155/2020/1646943. PMID: 32565838; PMCID: PMC7256708.

• Kim, Ki-Hyun et al. “Airborne bioaerosols and their impact on human health.” Journal of environmental sciences (China) vol. 67 (2018): 23-35. doi:10.1016/j.jes.2017.08.027.

• Tibbett, Mark et al. “Identifying potential threats to soil biodiversity.” PeerJ vol. 8 e9271. 12 Jun. 2020, doi:10.7717/peerj.9271.