Pollution's Dark Side: Kidney Tumors And Their Causes

Environmental pollution has been linked to an increased risk of several diseases, including cancer, heart disease, and lung disease. While the impact of pollution on kidney health is often overlooked, it is a significant contributing factor to kidney disease. Air pollution, in particular, has been associated with an increased risk of kidney disease-related events, including hospital admissions and death, especially in vulnerable populations. Additionally, long-term exposure to even low to moderate levels of air pollution can lead to chronic systemic inflammation and oxidative stress, which are known to contribute to the development of kidney disease.

Heavy metals, such as mercury, lead, and cadmium, are common environmental pollutants that have been linked to kidney damage and the development of chronic kidney disease (CKD). These metals can contaminate food, water, and soil, leading to increased exposure among the general population. For example, cadmium exposure often occurs through the consumption of rice grown in soil containing the metal, while lead exposure can occur through old plumbing or industrial activities such as battery manufacturing.

Other pollutants, such as herbicides and pesticides, have also been associated with an increased risk of CKD, particularly in farm workers who have heavy exposure to these chemicals. Furthermore, air pollution has been linked to an increased risk of kidney cancer, with studies suggesting a positive association between air pollution exposure and bladder and kidney cancer risk.

Overall, the evidence highlights the significant impact of environmental pollution on kidney health and the need for further interdisciplinary research in this area.

Heavy metals in food, water, and industry

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. They are used in a variety of industrial, domestic, agricultural, medical, and technological applications, leading to their wide distribution in the environment.

Food

Heavy metals such as arsenic, cadmium, lead, and mercury are naturally occurring chemical compounds that can be present in varying levels in the environment, including soil, water, and the atmosphere. They can also be present as residues in food due to their presence in the environment, as a result of human activities such as farming, industry, or car exhausts, or from contamination during food processing and storage.

Arsenic, for example, can be found in contaminated drinking water, pesticides, seafood, folk or alternative remedies, and products used for wood preservation. Cadmium exposure often comes from food, such as rice grown in soil with cadmium in it, and cigarette smoke. Mercury exposure occurs through the consumption of contaminated water, fresh fish from a contaminated source, predatory ocean fish, and seafood. Lead compounds are commonly used in gasoline, batteries, pipes, ammunition, paints, ceramic glazes, and water contaminated by lead pipes.

Water

Water can be contaminated with heavy metals due to industrial processes, improper waste disposal, and natural phenomena such as weathering and volcanic eruptions.

Industry

Heavy metals are widely used in various industrial activities and applications, which can lead to environmental contamination and human exposure. Some common sources of heavy metals in industry include:

• Metal processing in refineries
• Coal burning in power plants
• Petroleum combustion
• Nuclear power stations
• Plastics
• Textiles
• Microelectronics
• Wood preservation
• Paper processing plants

Health Effects

The accumulation of heavy metals in the body can lead to harmful effects over time, including an increased risk of chronic kidney disease and cancer. Heavy metals can cause cellular damage, induce oxidative stress, and interfere with cellular organelles and components such as cell membranes, mitochondria, lysosomes, and nuclei.

• Arsenic: Acute arsenic-induced renal intoxication can lead to acute tubular necrosis and tubulointerstitial nephritis. Chronic exposure to arsenic has been associated with the development and progression of chronic kidney disease due to arsenic-induced oxidative stress.
• Cadmium: Cadmium has a long half-life in the body and can accumulate in the proximal tubules of the kidney, impairing tubular function and protein reabsorption. It is a nephrotoxic environmental pollutant, and exposure can result in symptoms such as low molecular weight proteinuria, glucosuria, aminoaciduria, hypercalciuria, and renal stones.
• Lead: Lead is the most common environmental nephrotoxicant. Exposure can cause oxidative stress in tubular and glomerular cells, leading to cellular apoptosis and changes in renal structure and function. Acute lead toxicity can cause proximal tubular injury, while chronic lead poisoning can lead to glomerular sclerosis, tubular atrophy, tubulointerstitial fibrosis, and reduced glomerular filtration rate.
• Mercury: Mercury readily accumulates in the kidneys and can contribute to both tubular and glomerular damage. Exposure to mercury has been associated with various renal manifestations, including membranous glomerulopathy, interstitial nephritis, acute tubular necrosis, and nephrotic syndrome.
• Uranium: Environmental exposure to uranium is mainly through the ingestion of contaminated groundwater, soil, and food. Occupational exposure can also occur through inhalation. Uranium toxicity primarily occurs in the kidneys, and exposure has been associated with glucosuria, aminoaciduria, microalbuminuria, β2 microglobulinuria, phosphaturia, and hypercalciuria.

Overall, heavy metals in food, water, and industry can have significant health impacts, and it is important to implement strategies to reduce exposure and prevent adverse effects.

Tobacco smoke

Research has shown that even a small number of cigarettes per day can significantly increase the risk of kidney cancer. The risk increases non-linearly with smoking intensity and duration. For example, a person smoking 30 cigarettes per day has a much higher risk of developing kidney cancer than someone smoking five. The risk also decreases over time after quitting smoking.

Secondhand smoke also increases the risk of kidney disease and cancer. Even non-smokers living with smokers are at a higher risk of developing these health problems.

Herbicides and pesticides

The Agricultural Health Study (AHS), a large prospective cohort study, has found associations between pesticide use and CKD. The study tracked the health of thousands of licensed pesticide applicators and their spouses in North Carolina and Iowa. The findings suggest that exposure to pesticides is a potentially modifiable risk factor for CKD.

Among the pesticides studied, several herbicides were associated with an increased risk of CKD, including pendimethalin, atrazine, dicamba, alachlor, metolachlor, and paraquat. The insecticides chlorpyrifos and chlordane were also linked to an increased risk.

The specific mechanisms by which these pesticides contribute to CKD development are not yet fully understood and require further investigation. However, the widespread use of these chemicals underscores the importance of using appropriate personal protective equipment and following best application practices to minimize potential exposures.

Air pollution

Particulate matter, a common air pollutant, has been identified as a risk factor for chronic kidney disease (CKD). Evidence suggests that exposure to particulate matter can lead to a decline in glomerular filtration rate (GFR) and an increased prevalence and incidence of CKD. Additionally, air pollution may exacerbate traditional kidney disease risk factors such as hypertension and diabetes, accelerating disease progression.

Several studies have found positive associations between air pollution exposure and bladder and kidney cancer risk. However, the evidence is mostly derived from occupational studies, and further research is needed to understand the impact of air pollution on the general population's risk of developing these cancers.

Overall, while the exact mechanisms are still being elucidated, the available evidence suggests that air pollution is a significant risk factor for kidney disease and cancer.

Aristolochic acid in plants and herbs

Aristolochic acid is a family of nitrophenanthrene compounds found in the roots and rhizomes of plants of the family Aristolochiaceae, particularly in the genus Aristolochia. Lower concentrations are found in the fruit and leaves. The family Aristolochiaceae includes the genera Aristolochia and Asarum (wild ginger), which are commonly used in Chinese herbal medicine.

The medicinal parts of each plant (i.e. stem, root, fruit) have distinct Chinese names. In traditional Chinese medicine, Aristolochia species are considered interchangeable with other commonly used herbal ingredients, and the substitution of one plant species for another is an established practice.

The use of AA-containing plants for medicinal purposes has a long history. Birthwort plants and the aristolochic acids they contain were common in ancient Greek and Roman medical texts, and were well-established as an herb in the fifth century BC. Birthworts appeared in Ayurvedic texts by 400 AD, and in Chinese texts later in the fifth century. In ancient times, it was used to treat kidney and urinary problems, as well as gout, snakebites, and a variety of other ailments.

However, aristolochic acids are carcinogenic, mutagenic, and nephrotoxic phytochemicals. The aristolochic acid occurring in Aristolochia species used in traditional herbal medicines has been reported to function as a phospholipase A2 inhibitor and as an antineoplastic, antiseptic, anti-inflammatory, and bactericidal agent.

The carcinogenic potential of aristolochic acid started to appear in the 1980s. In addition to renal damage, safety studies reported an increased incidence in pathologic lesions indicating aristolochic acid–induced carcinogenicity in rodents orally administered aristolochic acid. The rodents developed multiple cancers, including lymphoma, as well as cancers in the kidney, bladder, stomach, and lung. Short-term studies resulted in tumors in the urinary tract in addition to the other renal pathological changes indicative of Chinese herbal nephropathy.

The International Agency for Research on Cancer (IARC), an arm of the World Health Organization, concluded that there was sufficient evidence to determine that aristolochic acid–containing herbs are carcinogenic in humans, thus classifying them as Group I carcinogens.

To this day, reports from around the world, especially in East Asia, continue to link the rapid onset of renal failure and/or renal cancer with the consumption of teas brewed from the ground root of these botanicals.

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