Pollution's Impact: Human And Animal Health At Risk

Pollution is a pressing issue that affects both human and animal health. It is caused by various factors, including sewage, exhaust fumes, trash, agricultural and lawn chemicals, and industrial and power plant emissions. These pollutants can have detrimental effects on the environment and the health of humans and animals.

Air pollution, for example, can harm wildlife in two main ways. Firstly, it affects the quality of their habitat and, secondly, it impacts the availability and quality of their food supply. Water pollution, on the other hand, can cause the death of aquatic animals and contaminate drinking water sources, leading to health issues in humans.

Additionally, climate change caused by pollution poses a significant threat to health and well-being. It is crucial to address these issues and implement measures to reduce pollution and mitigate its impacts on human and animal health.

Respiratory and cardiovascular diseases

Air pollution is a major concern and has a serious toxicological impact on human health and the environment. It has been linked to several respiratory and cardiovascular diseases, with evidence suggesting a strong correlation between air pollution and the development of these diseases.

Respiratory Diseases

Air pollution has been linked to several respiratory diseases, including respiratory infections and inflammations, asthma, lung cancer, and chronic obstructive pulmonary disease (COPD). Particulate matter (PM), ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead are among the main air pollutants that impact respiratory health.

PM, in particular, has been associated with increased respiratory symptoms, decreased lung function, and a higher incidence of chronic cough, bronchitis, and conjunctivitis. Ozone (O3), another pollutant, can increase the risk of respiratory diseases, especially asthma. Additionally, nitrogen oxides are deep lung irritants that can induce pulmonary edema if inhaled at high levels.

Cardiovascular Diseases

Air pollution has also been implicated in the development and exacerbation of cardiovascular diseases. Fine particulate matter (PM2.5), with diameters less than 2.5 µm, has been identified as a significant contributor to cardiovascular events, including heart attacks and strokes. Research has shown that exposure to increased concentrations of PM2.5 over a short period can trigger cardiovascular issues, while long-term exposure can lead to an increased risk of cardiovascular mortality and decreased life expectancy.

Additionally, air pollution has been linked to changes in white blood cell counts, which can affect cardiovascular functions. Studies have also suggested a close relationship between hypertension and air pollution exposure, particularly exposure to high levels of nitrogen dioxide (NO2).

Impact on Animals

Air pollution can harm wildlife by affecting the quality of their environment and habitat, as well as the availability and quality of their food supply. Pollutants such as acid rain, heavy metals, persistent organic pollutants (POPs), and other toxic substances can contaminate the soil, water, and food sources, leading to health issues and even death in animals.

For example, acid rain can change the chemistry of soils and water bodies, making them too acidic for some animals to survive. Heavy metals, such as mercury, can be transported through the air and accumulate in the tissues of animals, leading to reproductive issues and increased vulnerability to diseases.

Overall, air pollution has far-reaching consequences for both human and animal health, with respiratory and cardiovascular diseases being among the most significant impacts.

Neuropsychiatric complications

Air pollution has been linked to a range of neuropsychiatric complications, including an increased risk of neurological and psychiatric disorders. The respiratory tract is a key portal of entry for pollutants, with inhalation allowing particles to pass through the nasal cavity and directly to the olfactory nerve and bulb, as well as other nerves and the lower respiratory tract.

Stroke

There is strong evidence of a causal link between air pollution and cardiovascular morbidity and mortality, including stroke. The risk of stroke is higher in areas where PM2.5 (fine particulate matter) levels are above the US EPA standard, but even lower levels of PM from local traffic exhaust sources can carry a risk. Modifiable risk factors, including indoor and outdoor air pollution, are responsible for 90% of the stroke burden globally.

Neurodegenerative Diseases

Air pollution has been associated with an increased risk of neurodegenerative diseases, including Alzheimer's, Parkinson's, and Amyotrophic Lateral Sclerosis (ALS). Exposure to air pollution, particularly fine particulate matter, has been linked to cognitive decline and the development of neurodegenerative diseases, with evidence suggesting that this process begins in early childhood. Living near major roads and long-term exposure to air pollution have been identified as risk factors for dementia, with higher risks among those who have never moved from urban locations.

Psychiatric Symptoms

Air pollution has also been implicated in the development of psychiatric symptoms and disorders, including depression, anxiety, and suicide. Increases in chronic exposure to fine particulate matter have been associated with a higher risk of depression, especially in older individuals. Additionally, air pollution has been linked to an increased risk of suicide, particularly in APOE4 carriers.

Mechanisms

The exact mechanisms by which air pollution contributes to neuropsychiatric complications are still being elucidated, but oxidative stress and inflammation are believed to play a crucial role. Oxidative stress occurs when there is an imbalance between the production of reactive oxygen species and the body's ability to detoxify them, leading to cellular damage. Inflammation, induced by the body's immune response to pollutants, can also damage neurons and disrupt cellular function.

In addition, air pollution can impair the blood-brain barrier, allowing harmful substances to enter the brain. Soluble particulate matter, such as metals and nanoparticles, can translocate across nerves and deposit in neural tissue, disrupting neural function. Activation of the sympathetic-adrenal-medullary (SAM) and hypothalamic-pituitary-adrenal (HPA) axes by inhaled pollutants may also contribute to neuroendocrine imbalances and neuroinflammation.

Skin diseases

Air Pollutants and Their Impact on Skin Health

Ultraviolet Radiation:

• The sun's UV rays include UVA, UVB, and UVC, with UVA and UVB reaching the Earth's surface.
• UVA exposure leads to extrinsic skin ageing (photoageing), characterised by coarse wrinkles, solar elastosis, and pigment irregularities.
• UVB is responsible for sunburn, while UVA and UVB contribute to skin cancer and immunosuppression.
• UV radiation, particularly UVA, combined with air pollutants like ozone, enhances skin damage.
• Ozone, nitrogen dioxide, and sulfur dioxide in the troposphere reduce the effects of shorter UV wavelengths, leading to reduced UV irradiance in polluted urban areas.

Polycyclic Aromatic Hydrocarbons (PAHs):

• PAHs are dangerous organic pollutants, often found in urban areas, and are among the components of particulate matter.
• They induce oxidative stress and are associated with extrinsic skin ageing, pigmentation, skin cancers, and acneiform eruptions.
• PAHs can be absorbed through the skin and are found in all human bodily fluids and hair.

Volatile Organic Compounds (VOCs):

• VOCs are emitted from various sources, including paints, vehicle emissions, and industrial facilities.
• They contribute to the formation of ground-level ozone and photochemical smog.
• VOCs have been linked to inflammatory skin conditions like atopic dermatitis and eczema, particularly when combined with sunlight and nitrogen oxides.

Nitrogen Oxides:

Nitrogen oxides, particularly nitrogen dioxide, are emitted from combustion sources and can cause oxidative damage to the skin and tissues.

Particulate Matter (PM):

• PM consists of complex mixtures of particles in the air, originating from factories, power plants, vehicle emissions, and natural sources like windblown dust.
• Nanosized particles from traffic sources are considered the most harmful, as they can penetrate the skin and generate oxidative stress, contributing to extrinsic skin ageing.

Ozone:

• Ozone is a gaseous oxidant that exists in the stratosphere and troposphere and is formed through the interaction of sunlight, hydrocarbons, VOCs, and nitrogen oxides.
• It induces oxidative stress, reduces antioxidant levels in the skin, and impairs the skin's barrier function, leading to inflammation.
• Exposure to ozone has been associated with skin conditions like urticaria, eczema, and contact dermatitis.

Cigarette Smoke:

• Cigarette smoke contains thousands of chemicals and is a significant source of oxidative stress and free radicals.
• It contributes to premature skin ageing, characterised by deeper periorbital wrinkling and skin discolouration.
• Smoking is associated with an increased risk of skin cancer, psoriasis, acne, and other skin conditions.

Strategies for Prevention and Protection:

• Reducing air pollution through the use of clean energy sources and environmental protections is essential.
• On an individual level, strategies such as cleansing the skin, using sunscreens, and adopting a diet rich in antioxidants can help protect against the detrimental effects of air pollution.

In summary, air pollution has far-reaching consequences for skin health, and it is crucial to recognise its role as a risk factor for various skin disorders.

Cancer

Air pollution is a major public health concern, and it has been linked to various types of cancer. While air pollution is closely associated with lung cancer, it may also have an effect on the risk of other cancers.

Lung Cancer

According to the World Health Organization (WHO), outdoor air pollution is a leading environmental cause of cancer deaths. Hundreds of thousands of lung cancer deaths worldwide are attributed to air pollution, making it the second leading cause of lung cancer after smoking. Air pollution contains various carcinogens, and when inhaled, these carcinogens can cause physical damage to cells, leading to inflammation, oxidative stress, and cell mutations.

Other Cancers

While the link between air pollution and lung cancer is well-established, the evidence for other types of cancer is less conclusive, and more research is needed. However, there is some evidence suggesting that air pollution may be a possible cause of bladder cancer, breast cancer, kidney cancer, colon cancer, and rectal cancer. Additionally, scientists are studying the potential link between air pollution and childhood leukemia.

Impact on Animals

Air pollution also affects wild animals, with cancer being linked to pollution in around 30 aquatic species. Skin cancer and liver cancer are frequent outcomes of living in contaminated waters in several fish species. Pollutants can suppress the immune system, increase susceptibility to cancer-causing pathogens, and cause long-term tissue damage, initiating oncogenic processes.

Reproductive and developmental harm

Impact on Animals

Air pollution can cause serious harm to wildlife in two main ways: it affects the quality of the environment or habitat in which they live, and it affects the availability and quality of their food supply.

Air pollution can alter the sex hormones/pheromones, sex differentiation, and reproductive timing of animals. For example, exposure to the herbicide diclofop-methyl has been found to inhibit sex pheromone production in the cotton bollworm moth by reducing fatty acid synthesis.

Air pollution can also have consequences for gametes. For instance, exposure to chemical-dispersing agents can reduce the fertilising capability of sperm in capelin fish.

In addition, air pollution can impact the ability of animals to locate potential mates by disrupting the production, transmission, and detection of signals important in sexual communication.

Impact on Humans

Air pollution has been linked to a decrease in spontaneous fertility in both animals and humans.

Air pollution can also impact the male gamete. Studies have found that various forms of air pollution have harmful effects on sperm quality. A statistically significant decrease in the daily production of spermatozoa has been reported along with an increase in abnormal sperm shapes in mice and rats exposed to car exhaust, notably from diesel vehicles.

Air pollution can also impact the female gamete. Very few studies have been carried out on the impact of air pollution on female reproductive parameters in spontaneous fertility, likely due to the difficulties involved in such studies.

Mechanisms of Action of Air Pollutants

Four possible mechanisms have been put forward in the literature for the mechanism of action of air pollutants on fertility:

• Hormonal changes due to an endocrine disruptor activity
• Oxidative stress induction
• Cell DNA alteration
• Epigenetic modifications

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