Why is malaria considered an infectious disease?
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Some of this chemicals are causes cancer especially the radioactive one.
What is Environmental assessment?
Which chemicals are radioactive?
Hazardous chemicals escape to the environment by a number of natural and/or anthropogenic activities and may cause adverse effects on human health and the environment.
Our industrialized society dumps huge amounts of pollutants and toxic wastes into the earth\'s biosphere without fully considering the consequences. Such actions seriously degrade the health of the earth\'s ecosystems, and this degradation ultimately affects the health and well-being of human populations. When environmental conditions are degraded such that the range of tolerance is exceeded, there will be a significant impact on human health.
For most of human history, biological agents were the most significant factor in health. These included pathogenic (disease causing) organisms such as bacteria, viruses, protozoa, and internal parasites. In modern times, cardiovascular diseases, cancer, and accidents are the leading killers in most parts of the world.
However, infectious diseases still cause about 22 million deaths a year, mostly in undeveloped countries. These diseases include: tuberculosis, malaria, pneumonia, influenza, whooping cough, dysentery and Acquired Immune Deficiency Syndrome (AIDS). Most of those affected are children. Malnutrition, unclean water, poor sanitary conditions and lack of proper medical care all play roles in these deaths.
In our industrialized society, chemical agents also have significant effects on human health. These include:
• Toxic heavy metals,
• Pesticides, and
• Endocrine disrupters.
Heavy metals (e.g., mercury, lead, cadmium, bismuth, selenium, chromium, thallium) are typically produced as by-products of mining and manufacturing processes. All of them biomagnify (i.e., they become more concentrated in species with increasing food chain level). Mercury from polluted water can accumulate in swordfish to levels that are toxic to humans.
When toxic heavy metals get into the body, they accumulate in tissues and may eventually cause sickness or death. Studies show that people with above-average lead levels in their bones have an increased risk of developing attention deficit disorder and aggressive behavior. Lead can also damage brain cells and affect muscular coordination.
Dioxins are organic compounds, usually produced as a byproduct of herbicide production. They are stable compounds and can accumulate in the environment. Dioxins also biomagnify through the food chain and can cause birth defects and death in wildlife. Although dioxin is known to be extremely toxic to mammals, its low-level effects on the human body are not well known.
The infamous Agent Orange used as a defoliant during the Vietnam war contained a dioxin component. Many veterans from that war suffer from a variety of medical problems attributed to Agent Orange exposure.
Pesticides are used throughout the world to increase crop yields and as a deterrent to insect-borne diseases. The pesticide DDT was widely used for decades. It was seen as an ideal pesticide because it is inexpensive and breaks down slowly in the environment. Unfortunately, the latter characteristic allows it to biomagnify through the food chain.
According to the World Health Organization, more than three million people are poisoned by pesticides each year, mostly in undeveloped countries, and about 220,000 of them die. Long-term exposure to pesticides by farm workers and workers in pesticide factories seems to be positively correlated with an increased risk of developing various cancers.
Endocrine disrupters interfere with the functions of hormones in the human body, especially those controlling growth and reproduction. They do this by mimicking certain hormones and sending false messages to the body. Because they are active even in low concentrations, endocrine disrupters may cause problems in relatively low doses.
Some of the effects include low sperm count and sterility in males. Since 1940, sperm counts have dropped 50% in human males, possibly the result of exposure to endocrine disrupters. Heavy metals, dioxins and pesticides may all be endocrine disrupters.