Disease
Whenever homeostasis is disrupted, bodily systems can respond and attempt to return to their normal state. Disease occurs when cells, or bodily systems cannot reestablish homeostasis. As a result structural, biochemical, and functional changes occur within cells, tissues, and organs. While many diseases are the result of genetic errors, most arise from the complex interaction of genetic variations and environmental factors. Environmental factors include chemical agents, toxins, pathogens, (viruses and bacteria in the air, water, or soil) and the individual’s life style.
Genetic Errors
Errors in the genetic code can be either at a single point (an error in one base), at a single gene, or involve a whole chromosome (deletion or addition of one complete chromosome); multigenic errors, however, cannot be isolated to a single gene or chromosome. These genetic diseases arise from internal malfunctions: their genesis is independent of environmental factors: they are solely dependent on the person’s genotype. Complex multigenic diseases can arise as a result of errors in the genotype, however they involve interaction with “environment.” In the case of these diseases, the genomic aberration creates a predisposition towards a disease. The exposure to toxins, pathogens, or the person’s life decisions will determine the incidence of the disease.
Pathogens
Pathogens are disease-causing microorganisms that invade the body and disrupt the proper functioning of bodily systems in a variety of ways. There are four major classes of pathogens: viruses, bacteria, protozoa, and helminthes. These pathogens live in a variety of environments, however they are most prevalent in water environments. Water borne microbial pathogens are the leading cause of death and disease in developing countries.
Microbial Water Borne Pathogens
Microbial enteric pathogens are implicated in a wide variety of diseases. These diseases are the result of ineffective wastewater treatment, which affects sanitation and hygiene. The death rates from the resulting infectious diseases affect mostly children in developing nations. Poor water quality accounts for 3.1% of deaths worldwide and 3.7% of all DALY (Disability Adjusted Life Years). It is estimated that 90% of the disease burden attributed to poor water quality occurs in developing nations, with 80% of the fatalities being children (Ashbolt). Cholera and typhoid are the most prevalent diseases caused by enteric pathogens, (World Health Organization), followed by various serogroups of rotaviruses, and parasitic protozoa. The diseases cause generally extreme cases of diarrhea resulting in dehydration, malnutrition, and eventually death. In developed societies, the risk of infection from these pathogens is relatively small given that the quality of water, sanitation, and hygiene limit the virulence of these infectious agents. Children, the aged and immunologically compromised remain at risk, however access to quality health technologies limits morbidity when infections arise.
Viruses
Viruses are obligate pathogens: they do not have the cellular mechanisms needed to self-replicate. They do however contain a segment of genome (either RNA or DNA), the necessary enzymes to invade a cell and use it to reproduce, and thence spread throughout the body.
Cancer
Water borne microbes are not a major source of disease in developed nations since water treatment, sanitation, and hygiene effectively reduce the incidence or enteric pathogens. In these nations, carcinogenic agents in the air, water, and soil contribute to the relatively high rates of cancer, which are major sources of mortality and disease. There are many (known and suspected), carcinogens that result from industrial processes, toxic waste, and secondary air pollution. Cancer arises as a result of mutations in our genetic code. While some cancers are the result of inherited defects, most are the result of acquired mutations occasioned by our contact with carcinogens in the environment. While most mutated cells are eliminated by our immune response, over time some survive. A cancerous tumor typically develops from a single mutated cell, however as the tumor grows, cells acquire new capabilities that allow them to aggressively reproduce, develop their own blood supply (angiogenesis), invade tissues and organs while evading apoptosis and all other signals that might limit their growth. There are two categories of genes that are implicated in all cancers: proto-oncogenes and tumor suppressor genes. In normal bodily functions, proto-oncogenes are responsible for signaling orderly and limited replication of cells, while tumor suppressor genes function to limit cell division. Oncogenes result from alterations in the genetic code of proto-oncogenes, which then trigger uncontrolled cellular replication. Mutations in tumor suppressor genes disable mechanisms that limit cell growth, or target cancerous cells for apoptosis. There are approximately 140 known cancer-causing genes (approximately 60 oncogenes and 80 tumor suppressor genes) that affect various cellular functions.
Exposure to environmental toxins
Hazardous Waste Disposal and Carcinogens
Data collected in recent years has shown an increase in the incidence of various types of cancers for residents exposed to hazardous wastes, (Johnson), those living in close proximity to hazardous waste disposal sites (Cancer Surveillance Program), or solid waste incinerators (Garcia-Perez, Fernandez-Navarro and Castello). Toxic wastes stored in landfills also leach into soils, groundwater, or (in the case of volatile compounds) vaporizes into the air (Bakare, Alimba and Alabi). Each of these forms of solid waste leachate is a potential carcinogen.
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