Human activity

Also of value is the study of the history of technology (24,25) that affords insights into the history of the development of civilization. The eadiest existing written records, treatises of crafts people and artists on the techniques and materials with which they worked, date back to medieval times (26—29). For prehistoric human activities, the record is in the objects which remain, and only through the study of these can knowledge in this regard be furthered. 

Human activity, particularly in the developing world, continues to make it more difficult to sustain the world s biomass growth areas. It has been estimated that tropical forests are disappearing at a rate of tens of thousands of hm per year. Satellite imaging and field surveys show that Brazil alone has a deforestation rate of approximately 8 x 10 hm /yr (5). At a mean net carbon yield for tropical rain forests of 9.90 t/hm yr (4) (4.42 short ton /acreyr), this rate of deforestation corresponds to a loss of 79.2 x 10 t/yr of net biomass carbon productivity. 

The NRC safety goal can be evaluated by comparison to the risks from accidents incurred from other human activities (Eig. 2) (29). The safety goal and the safety record of the nuclear power industry indicate much lower societal risks from commercial nuclear power than from a wide range of other common human activities. 

Ideally the historical record of stream water quaUty would extend back to a time when human activities in the drainage basin had no significant effects. This "pristine" condition had probably already passed in most U.S. rivers before any organized water quaUty studies were made, as concern about apparent stream pollution was commonly a motivating factor in starting such studies (see Water, pollution). 

Chlorine plays a less significant role in chemical weathering processes than do sulfur and carbon. Most geochemists beHeve that much, or most, of the chloride in stream water in coastal areas is derived from sea salt that is carried landward or deposited by rainfall. Farther inland, however, a major part of the chloride loads in streams is the result of human activities. 

The efficiency of the weathering of rocks in using carbonic acid produced in the carbon cycle is affected by various hydrologic, environmental, and cultural controls. The fact that the principal anion in fresh surface water worldwide almost always is bicarbonate attests to the overriding importance of this process. Exceptions are systems in which evaporite minerals are available for dissolution by groundwater or where human activities are major sources of sulfate or chloride inflow. 

Geochemical studies of sulfate ia streams have beea approached ia various ways. For example. Ref. 17 is a review of Hterature oa sources of sulfate ia the dissolved loads of streams, especially ia areas where developmeat effects are likely to be stroag. It was coacluded that for North America as much as 60% of the average yield of sulfate carried to the ocean is related to human activities. This study assigned a higher proportion of the total yield of sulfate ia European streams to human sources, but for other continents it was thought the effects of human activities to be relatively minor. 

The influence of human activities in a stream drainage basin can be relatively simple and direct, as in the disposal of soluble organic and inorganic waste, or more subtie and complex, as in the conversion of prairie or forest land to agricultural use. Such effects can be expected to increase as population density and agricultural, industrial, and mining activities increase. 

The products of human activities find their way into the environment and disturb ecosystems. Pollution has altered the surroundings to the detriment of humanity. In the last several decades, the poUutional load has increased, and its character has changed (see Water—pollution). 

In addition to considering the external environment, recommendations for the internal environment have been set. Every room in which human activity is required has maximum limits for noise (85—90 dB), carbon dioxide, solvents, radiation, temperature, etc. 

Indoor air contaminants can originate within the building or be drawn in from outdoors. If contaminant sources are not controlled, problems can arise, even if the HVAC system is properly designed and well-maintained. Sources can be from outside the building from operating equipment, from human activities, and other or miscellaneous sources. Sources outside a building include contaminated outdoor air, emissions from nearby sources, soil gas, or moisture or standing water. 

Natural Conditions conditions substantially unaltered by humans or human activities, as applied in the context of visibility, natural conditions include naturally occurring phenomena that reduce visibility as measured in terms of light extinction, visual range, contrast, or coloration. 

Air flow technologies that achieve and maintain a safe, healthy, productive and comfortable indoor environment in premises and occupied enclosures where this need is determined not only by human occupancy, normal human activities, and construction and finishing materials but also, and often primarily, by other factors, for example, production processes... 

Vision is vital for human activities, and eyes are very sensitive to a number of toxic insults induced by chemical compounds. The most serious outcome is permanent eye damage which may be so severe as to cause loss of vision. The eye consists of the cornea and conjunctiva, the choroid, the iris, and the ciliary body. It also contains the retina, which is of neural origin, and the optic nerve. The retina contains photoreceptors, a highly specific light-sensitive type of neural tissue. The eye also contains the lens and a small cerebrospinal fluid system, the aqueous humor system, that is important for the maintenance of the steady state of hydration of the lens and thus the transparency of the eye. 

Pollutant load Room height Heat load Human activity level Common air supply methods Type of process... 

Air is made up of a mixture of different gases and material from natural processes such as wind erosion, evaporation from the sea, earthquakes, and from human activity in the form of combustion products from processes and vehicles. 

Studies of atmospheric particles show that their distribution is often birno-dal i.e., the particles are made up of rwo separate fractions, one with fine and one with coarse particles (Fig. 9.1). The coarse particles, from about 2.5 pm upward, are made up of natural dust from the effect of wind, erosion, plants, volcanoes, etc. The finer fraction is made up of particles smaller than 2.5 pm and consists primarily of particles from human activity, combustion, traffic, and processes. 

Advocates of the global approach would argue that human activities are essentially goal-directed (the cognitive view expressed in Chapter 2), and that this cannot be captured by a simple decomposition of a task into its elements. They also state that if an intention is correct (on the basis of an appropriate diagnosis of a situation), then errors of omission in skill-based actions are imlikely, because feedback will constantly provide a comparison between the expected and actual results of the task. From this perspective, the focus would be on the reliability of the cognitive rather than the action elements of the task. 

Treating a body of water as a completely mixed system can be a valuable approach for estimating the effects of human activities,... 

Examination of the risks of common human activities demonstrates...a lifetime risk of 1 in 100,000 or more is within tlie realm of, or orders of magnitude below, everyday risks tliat generally do not cause undue concern. These are risks tliat people, while they are aware of them and may luavc some concern or fear over them, do not in general alter tlieir behavior to avoid... the risks from many activities greatly exceed the level of 1 in 100,000. 

Air is the source of six industrial gases, N2, O2. Ne, Ar, Kr and Xe. As the mass of the earth s atmosphere is approximately 5 X 10 million tonnes, the supply is unlimited and the annual industrial production, though vast, is insignificant by comparison. The composition of air at low altitudes is remarkably constant, the main variable component being water vapour which ranges from 4% by volume in tropical jungles to very low values in cold or arid climates. Other minor local variations result from volcanism or human activity. The main invariant part of the air has the following composition (% by volume, bp in parentheses) ... 

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