BIOLOGICAL POLLUTANTS: COMPONENTS, TYPES AND CONSEQUENCES - ENVIRONMENT - 2025

The biological contaminants are those living organisms or products derived from these invading means producing unwanted by humans effects. Organisms that are part of all known taxonomic groups such as bacteria, archaea, protists, fungi, plants and animals can act as biological contaminants.

These pollutants affect the environment in general, causing problems for the soil, water, air, food, infrastructure and work spaces. Weed plants, pathogenic fungi and nematodes are found in agricultural soils, while pathogenic bacteria and protists are a serious threat to public health in water.

Structure of the influenza virus (flu), a widely spread biological contaminant.

Air is also a medium susceptible to biological contamination, as well as an efficient vehicle for transporting pollutants. Airborne viruses, bacteria, and fungal spores are transported long distances.

On the other hand, organisms such as bacteria, protozoa, fungi, insects, and mammalian excreta contaminate food and drinking water. Likewise, there are biological contaminants in work environments, educational centers, health centers and homes.

The presence of biological pollutants results in public health problems that imply economic losses in prevention and remediation. Food production is also affected by biological pollutants that affect crops or deteriorate already processed foods.

Components of biological contaminants

Biological pollutants are made up of living organisms and by products derived from their metabolism. Among living organisms, all biological kingdoms are represented and, in the case of metabolic derivatives, toxins and metabolic wastes (feces and urine) stand out.

- Living organisms

Virus

Although in the strict sense viruses do not fit the definition of life, they are normally considered in this area. Thus, viruses are high-impact biological contaminants due to their reproductive and invasive capacity.

Viral pandemics are becoming more frequent, such is the case of the recent crisis with pneumonia caused by the 2019-nCoV coronavirus. Depending on the type of virus, these can spread through the air, by contact, or by vectors such as mosquitoes (mosquitoes).

Bacteria and archaea

Bacteria are another of the main biological pollutants that cause health problems in humans, animals and plants. They are spread by water, food, through the air or by direct contact. They can contaminate all environments: soil, water, food and infrastructure and objects.

Protozoa

Protozoa can contaminate aquatic environments, the soil, and even be transported in atmospheric dust. Some form cysts that make them resistant to high temperatures, desiccation, and even disinfection.

Protozoan causing meningoencephalites (Naegleria fowleri) (Source: Photo Credit: Content Providers (s): CDC / Dr. Govinda S. Visvesvara

Protozoa like Acanthamoeba cause encephalitis and corneal conditions, others like Naegleria fowleri cause serious diseases like primary amoebic meningoencephalitis. Many other species are intestinal pathogens that contaminate through feces.

Mushrooms

There are many species of pathogenic fungi that pollute the environment, affecting human, animal and plant health. By spreading by spores, they are efficiently dispersed through the air, and they also pollute soil and water.

Plants

Many plant species act as weeds, contaminating agricultural soils and affecting crop productivity. They are also a reservoir for other contaminating organisms such as viruses, fungi, bacteria and insects. Weeds affect crops in the soil and bodies of water, where they participate in the eutrophication process.

Animals

Various animal species are pests of crops and animals, as well as humans and can be vectors of diseases. Insects are the most problematic group in this regard, with blood-sucking species such as lice, ticks, fleas, and mosquitoes.

Likewise, rodents, especially domestic ones such as the common rat and mice, are important pests. In turn, the excreta and urine of these animals contaminate food and transmit diseases.

- Metabolic derivatives

On many occasions the agent of biological contamination is not directly the living organism, but products derived from its metabolism.

Toxins

Species of bacteria, fungi, algae, plants and animals produce toxins as defense, which once in the environment become pollutants. They can be transferred along trophic webs, affecting biodiversity and humans.

Red tide. Source:

An example is toxic algal blooms (red tides) which are population explosions of toxic phytoplankton algae due to ecological imbalances. The populations form patches covering extensive marine areas, they poison various aquatic organisms that affect it when consumed by humans.

Feces and urine

The most common case in this line is the contamination of stored food by the feces and urine of rodents. For example, leptospirosis, a disease caused by the bacteria Leptospira interrogans, is spread by coming into contact with the urine of rats or other animals.

Protein

Although rare, certain structural components of living things can also be pollutants. Such is the case of the prions that cause bovine spongiform encephalopathy or 'mad cow disease'.

It is a defective protein that conditions a degenerative picture of the central nervous system, causing death. It affects both animals and humans by being transmitted through the consumption of infected meat.

- Genetic contaminants

With the development of genetic engineering, particularly of genetically modified organisms, a new type of biological contaminant appears. These are genes that unplanned are integrated into the genome of another organism other than its species, and can cause problems for humans.

Unwanted results

Beyond human manipulation, nature takes its course and genes inserted into one species can be transferred to another unwanted one. For example, a herbicide resistance gene included in a cultivated species that is transmitted to a weed-related species.

Another potential problem is the inclusion of a gene from one species that causes allergy to a population segment in another species. If the individual does not have adequate information, this can lead to serious health problems.

Types of biological contaminants

Biological pollutants can be classified by both the polluting organism and the polluting medium. In the latter case, these pollutants invade all the environments where the human being develops.

Biological contaminant. Source: Centers for Disease Control, United States

- Biological soil pollutants

Soils are contaminated with fungi, bacteria, protozoa, weeds and animals such as nematodes among others. These organisms cause health problems in crops, animal production systems and in human health.

Soil fungi, bacteria and nematodes are the cause of agricultural losses by affecting the root systems of plants.

Intestinal diseases

Contact with soil contaminated by protozoa and flatworms is one of the main sources of childhood intestinal diseases. This type of disease is the main cause of infant mortality in the world.

- Biological water pollutants

Water is a medium very susceptible to contamination, especially by biological pollutants that achieve an adequate vital environment and dispersal medium. Bacteria, protozoa and animals are found in water bodies as biological contaminants in different contexts.

Human pathogens

Bacteria, protozoa, and human pathogenic animals such as flatworms (tapeworms and others), reach the water mainly through contaminated excreta.

Toxins and excreta in the water

The water can be contaminated with biological toxins, for example those contained in toxic algae of phytoplankton in toxic algal blooms. An example is the dinoflagellate Gymnodinium catenatum, which produces a paralyzing saxitoxin.

Causal agent of toxoplasmosis (Toxoplasma gondii). Source:

Animal excreta and feces in water are also carriers of pathogens such as the protozoan Toxoplasma gondii (toxoplasmosis). Schistosomiasis or bilharzia is a disease that is contracted in waters infected by human excreta and is caused by flatworms of the genus Schistosoma.

- Biological air pollutants

Air is a means of dispersal of biological pollutants, with viral particles, bacteria, fungal spores and pollen grains in suspension. The case of pollen grains and spores is particularly relevant as they cause allergies and respiratory diseases.

- Biological contaminants in food

As living matter is the natural substrate for many living organisms, food is susceptible to biological contamination.

Bacteria and fungi are the main contaminants in food, many of them capable of causing illness in humans.

Bacterial food poisoning

Most cases of food poisoning are caused by bacteria in food or water. Among the most common are those caused by Escherichia coli, Salmonella species, and Staphylococcus.

Microscopic view of Escherichia coli bacteria

Toxins and organic waste

In some cases, biological contaminants in food can secrete deadly toxins, such as the bacterium Clostridium botulinum. The bacteria that cause botulism can contaminate any food, being very resistant to high temperatures. It is capable of producing botulinum neurotoxin, considered the most powerful that exists.

Clostridium botulinum Source: EAS

Fungi, when contaminating food, can also secrete mycotoxins, such as aflatoxins that have carcinogenic and mutagenic effects. Food can also be contaminated by the excreta and urine of pest animals such as rodents.

When contaminating food warehouses in search of food, rodents disperse their feces and urine, contaminating food products. In particular, the urine of mice and rats carries Hantavirus, leptospirosis and Salmonella.

- Biological contaminants of infrastructures, homes and work environments

Biological contaminants, such as bacteria, fungi, insects, rodents, and others are a major problem in human environments. In addition to being disease transmitters, they deteriorate infrastructures, render useless spaces and hinder work activities.

Medical centers

In medical centers, contamination with bacteria and fungi represent a serious problem, especially in areas that require total asepsis, such as operating rooms. In health centers without adequate hygiene, cases of nosocomial pneumonia are common, which is pneumonia contracted in the health center itself.

It has been pointed out that about 40% of in-hospital health complications are related to biological contamination of the center. This is an important cause of death, especially when it comes to bacteria that are multi-resistant to antibiotics such as Pseudomonas aeruginosa 35.

Sick building syndrome

The concept of sick building syndrome generates that deteriorated infrastructures present chronic problems of biological contamination. Among the most characteristic biological contaminants of this syndrome are viruses, fungi, bacteria and mites.

Consequences

Public health

The main consequence and the greatest impact are the affections to human health caused by biological pollutants. Infectious contagious diseases are one of the main diseases and are caused by biological agents that contaminate all types of environments and foods.

Provision of food

Biological contaminants in the form of pests and weeds affect the yield and productivity of crops and farm animals. Similarly, food reserves decrease when consumed in storage or contaminated.

Drinking water

Water is a vital element for life and the biological pollutants present in it make it dangerous for consumption. Currently humanity faces a deficit of drinking water, so that the contamination of the few available sources is a global problem.

Ecological imbalances and loss of biodiversity

Biological pollutants are involved in a large part of the environmental alterations that cause ecological imbalances. This in turn results in the loss of biodiversity, by reducing populations and even extinction of species.

The contamination of areas with exotic species is an important cause of the disappearance of local species through predation or advantageous competition. For its part, eutrophication is one of the main problems in aquatic ecosystems, caused by an excessive entry of nutrients into the environment.

Housing, work environment and infrastructure

The areas of housing, basic services and human work are deteriorated and even disabled by biological pollutants.

References

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