Ionizing Radiation Effects and Their Risk to Humans

The radiation affects human body in highly complicated processes. Various degrees of biological effects, from damage to death of living tissues, involve a number of pathological changes in human cells.

When exposed to ionizing radiation, large molecules such as nucleic acid and proteins in the cells will be ionized or excited. This may cause changes in the molecular structures which then affect the function and metabolism of the cells. Laboratory experiments have demonstrated that ionizing radiation can cause breakage of the DNA chain or can deter cell replications. In addition, the production of harmful free radicals (e.g. OH^-1, H⁺ etc.) by the ionization of water molecules due to radiation may lead to changes in OH molecules that are biologically important for the functioning of cells.

Although radiation can cause damage to living tissues, human cells however can repair the damage through natural metabolic processes if the absorbed dose is not high. Recovery of cells depends on the degree of initial damage and may be different for different individuals.

Understanding the effects of radiation on human bodies provide useful information for the development of radiation protection measures. A quantitative measure of the hazards induced by radiation is the "risk factor". Press here for details.

Ionizing Radiation Effects

The deleterious effect ionizing radiation has on human tissue can be divided into two types: non-stochastic (deterministic) or stochastic effects.

Deterministic (Non-Stochastic) Effects

Deterministic effects are caused by significant cell damage or death. The physical effects will occur when the cell death burden is large enough to cause obvious functional impairment of a tissue or organ.

Examples

1. Skin Erythema/Necrosis/Epilation
Erythema occurs 1 to 24 hours after 2 Sv have been received. Breakdown of the skin surface occurs approximately four weeks after 15 Sv have been received. Epilation is reversible after 3 Sv but irreversible after 7 Sv and occurs three weeks following exposure.

2. Cataract
Cataract occurs due to accumulation of damaged or dead cells within the lens, the removal of which cannot take place naturally. Cataract occurs after 2 to 10 Gy have been received, but may take years to develop.

3. Radiation Sickness
Radiation sickness (correctly termed acute radiation syndrome) involves nausea, vomiting, and diarrhea developing within hours or minutes of a radiation exposure. This is due to deterministic effects on the bone marrow, GI tract, and CNS.

4. Stochastic Effects

Stochastic effects occur due to the ionizing radiation effect of symmetrical translocations taking place during cell division.

Examples

Cancer

2. Over time, anecdotal evidence suggested that ionizing radiation could cause cancer. However, reliable evidence has only relatively recently become available. Data from the Radiation Effects Research Foundation on individuals exposed to radiation from the atomic bombs in Hiroshima and Nagasaki have shown an increased relative risk of developing malignancy (leukemia, oral cavity, esophagus, stomach, colon, lung, breast, ovary, urinary bladder, thyroid, liver, non-melanoma skin, and nervous system) as a result of radiation exposure. As such, multiple bodies, including the U.S. Department of Health and Human Services, have classified ionizing radiation as a human carcinogen.

39. Global dangers of the 21 century: demographic, ecological, social

Demography has a somewhat undefined but large influence on investment markets. A greater understanding of world population trends, therefore, can provide some clues as to what may power markets in the 21^st century.The two biggest global trends now are, firstly, that developed markets have ageing populations (and even a shrinking population in Japan’s case). The other is that young, working cohorts are reaching their economic prime and boosting growth in emerging markets. These trends have consequences from the top down and the bottom up.Let’s start with the macro implications. It will be expensive and perhaps painful, but developed countries can afford to support their ageing populations. Some emerging markets, however, may struggle.This is especially the case in China due to its one-child policy (which is now being relaxed). The draconian measure may have helped the country control its growth so far. But critics suggest that it simply postpones economic problems and will mean a generation of Chinese people will have to support two parents alone. Putting it simply, China must get rich before it gets old. Investors must bet on whether it can do that.Anyone who doubts demographics’ macro influence on investment markets should study the correlation between the passage of the baby-boomer generation through the decades and US equity valuations.The US baby-boomer population is so large at about 80 million people that any common behaviour can be powerful. Through the 1990s, this group was at the peak of its earning and savings potential.

However, the fact that people are living longer now needs to be considered. In the UK, the odds that at least one member of a 65-year-old couple will live to 93 are 50%. So some of the baby-boomers’ vast collective wealth may end up in equities at some point, simply to help their retirement funds last as long as they do.At an industry or company level, demographic factors are perhaps less contentious. At the moment, the clearest demographic-inspired opportunities appear to be in healthcare and consumer industries.The healthcare sector covers many companies, from drugs, through replacement body parts, to long-term care providers who offer products and services to ageing populations.The consumer sector caters to the growing number of wealthier younger populations, especially, but not exclusively, in the developing world. Examples include new technologies (or affordable versions of existing technologies), sportswear, luxury goods and education services.So while analysis of the world’s changing demographics is usually framed as a problem for governments, for investors it need not be.

Ecological disaste

An ecological, such as world crop failure and collapse of ecosystem services, could be induced by the present trends of overpopulation, economic development, and non-sustainable agriculture. Most of these scenarios involve one or more of the following: Holocene extinction event, scarcity of water that could lead to approximately one half of the Earth's population being without safe drinking water, pollinator decline, overfishing, massive deforestation, desertification,climate change, or massive water pollution episodes. A very recent threat in this direction is colony collapse disorder,^[43] a phenomenon that might foreshadow the imminent extinction^[44] of the Western honeybee. As the bee plays a vital role in pollination, its extinction would severely disrupt the food chain.

40. The total population of humans has risen at a rapid rate, partly because of the removal of natural checks on the population, such as disease. The earth has finite resources, increasing human population and consumption places severe stress on natural processes that renew some resources and deplete those resources with cannot be renewed.

A. Increasing numbers:

-results from an increased human life span

- health advances largely led to this

B. Food: shortage and inadequate nutrition lead to starvation and malnutrition

-population growth is outpacing food production in many world regions

-starvation: body lacks sufficient calories for maintenance

-malnutrition: diet lacks specific substances needed by the body

C. Soil is much loss of fertile topsoil due to erosion and poor management

D. Water: cutting forests has led to increased, uncontrolled runoff

E. Wildlife: much destruction and damage has been done to many species (hunting and fishing)

F. Fossil fuels: are becoming rapidly depleted to air pollution problems

41. Human impact on the environment or anthropogenic impact on the environment includes impacts on biophysical environments, biodiversity, and other resources. The term anthropogenic designates an effect or object resulting from human activity. The term was first used in the technical sense by Russian geologist Alexey Pavlov, and was first used in English by British ecologist Arthur Tansley in reference to human influences on climax plant communities.^[3]The atmospheric scientist Paul Crutzen introduced the term "anthropocene" in the mid-1970s.^[4] The term is sometimes used in the context of pollution emissions that are produced as a result of human activities but applies broadly to all major human impacts on the environment.^[5]

Causes

Technology

The applications of technology often result in unavoidable environmental impacts, which according to the equation is measured as resource use or pollution generated per unit GDP. Environmental impacts caused by the application of technology are often perceived as unavoidable for several reasons. Thus, technologies can create “order” in the human economy (i.e., order as manifested in buildings, factories, transportation networks, communication systems, etc.) only at the expense of increasing “disorder” in the environment. According to a number of studies, increased entropy is likely to be correlated to negative environmental impacts.^{[7][8][9][10]}

Agriculture

The environmental impact of agriculture varies based on the wide variety of agricultural practices employed around the world. Ultimately, the environmental impact depends on the production practices of the system used by farmers. The connection between emissions into the environment and the farming system is indirect, as it also depends on other climate variables such as rainfall and temperature.

Fishing

The environmental impact of fishing can be divided into issues that involve the availability of fish to be caught, such as overfishing, sustainable fisheries, and fisheries management; and issues that involve the impact of fishing on other elements of the environment, such as by-catch.

These conservation issues are part of marine conservation, and are addressed in fisheries science programs. There is a growing gap between how many fish are available to be caught and humanity’s desire to catch them, a problem that gets worse as the world population grows.

Similar to other environmental issues, there can be conflict between the fishermen who depend on fishing for their livelihoods and fishery scientists who realize that if future fish populations are to be sustainable then some fisheries must reduce or even close.^[12]

Irrigation

The environmental impact of irrigation includes the changes in quantity and quality of soil and water as a result of irrigation and the ensuing effects on natural and social conditions at the tail-end and downstream of the irrigation scheme.

The impacts stem from the changed hydrological conditions owing to the installation and operation of the scheme.

Date: 2015-12-24; view: 909