BIOFISIKA LINGKUNGAN

Biofisika Lingkungan Tentu Sangat Kompleks. Akan tetapi dari kompleksitasnya salah satu bagian yang menarik dan penting adalah biofisika dalam skala makroskopik, khususnya untuk biofisika kerja. Dalam Konteks ini konsep fisika yang penting adalah aplikasi Hukum Kekekalan Energi ketika seseorang berinteraksi dengan lingkungan fisik dan peralatan yang digunakan dalam suatu sistem kerja.

In Anonymous (2007) suggested that biophysics is the study of biological phenomena using the methods and concepts of physics, whereas in Anon (2005) suggested that biophysics is the interdisciplinary study of the phenomenon and biological problems using the principles of and techniques of physics. Biophysics relies on techniques derived from physics, but focused on biological problems.

Referring to the definitions that have been raised about the biophysics, so in the context of a worker who does outdoor activities, it can be seen as a biophysical study of biological phenomena on a worker who interacts with the local physical environment while doing work activities by using the principles, concepts, and methods of physics. In this case, Campbell (1977) called the study of physics in this context as the biophysical environment. According to Campbell (1977) developments in the field of environmental biophysics primarily focused on two areas namely:

1. Use of mathematical models to quantify the rate of heat and mass transfer, and
2. Use the continuity equation which has led to the analysis of energy balance.

Therefore, it can be argued that in the environmental biohysics learnt about how is the application of physics concepts on the interaction between living organisms with their physical environment, so in this context to learnt about the application of physics concepts on the interaction between workers and their physical environment when doing outdoor activities.
In a working system (Corlett and Clark, 1995), significant interaction not only between human and physical environment but also with tools and equipment used when working.The third form of interaction is illustrated in the figure below.

Take for example a student performs a field activity. Microclimate that consists of solar radiation, air temperature, air humidity, and wind speed which is the element of physical environment, become very important as an influential factor. In addition, tools and equipment in use is also decisive. The most important equipment is usually suit, and other equipment such as protective clothing (PPD) as hats, umbrellas, jackets / coats, and included here is a shoe. The equipment used will be adjusted to the goal of activity. For the field practicum activities the used equipment is equipment associated with the unit of practicum activity planned.

Phisical process about the influence microclimate, tools, and instruments used against the body of worker is biophysical processes.
Biophysical concept that is important in the biophysical process in this context are the law of conservation of energy. According to Campbell (1977) concept of conservation of energy, which is also commonly written in the form of continuity equation, the advanced application of environmental biophysics at last leads to the analysis of energy balance.

Energy balance analysis can be done by using a system approach. By looking at human body as a system, Havenith (1999, 2002), Blazejczyk (2000), Brake and Bates (2002) and Epstein and Moran (2006) describes the heat balance equation for the human body as the following equation,

Heat stored = heat produced – heat lost = (metabolic rate – external work) – (conduction + radiation + convection + evaporation + respiration)

The factors that state lose body heat, as has been stated in the above equation for the path of conduction, convection, and radiation, followed the general equation of transfer or heat transfer (Havenith, 2004; Campbell, 1977; Monteith and Unsworth, 1990) in which it’s general form of equation can be written as,

heat lost = (gradient x surface area)/risistance

From this equation it can be stated that for each path; conduction, convection and radiation, the amount of heat transferred depends on the driving force, the temperature gradient and vapor pressure, body surface area involved and the resistance in which the heat flow, which can be clothing insulation.

According to Havenith (1999, 2001, 2002, and 2004) the processes of heat loss and heat production are directed to the energy balance to maintain the normal body temperature of about 37 0C. This value is achieved by balancing the amount of heat produced in the body with the amount of heat lost. The following image shows the schematic representation of the path forms of energy that occurs when workers doing outdoor activities such as field practicum.

Heat production is determined by metabolic activity. At the break, the heat produced by the body for basic functions such as respiration and body's heart function by providing the body cells of oxygen and food (Nutrients) is required in carrying out the basic functions. At the time of performing the work activity, the needs of the active muscles against oxygen and food increases, and as a result of metabolic activity also increased. When the active muscle cells burn food for mechanical activity, part of the energy released to the outside of the body as external work, but most are released into the muscle as heat. When the heat is not released the temperature of the body will increase up to a lethal level.

Furthermore Havenith (1999, 2002) suggests, for the heat lost from the body, there are a few paths. The path with a small role is conduction. Conduction only becomes an important factor for people working in the water, or people who work for handling cold products or working in the supine position where the bodies come into contact with heat transfer medium. More important path for heat loss are convection, when the cooler air flows along the surface of the skin. Therefore, heat is transferred from the skin into the surrounding air. The heat will also be transferred in the form of electromagnetic radiation, or the so-called long-wave radiation. When there is a difference between body surface temperature and surface temperature of the object or objects around him there will be a transfer of heat by radiation..

Finally, the body also has other paths to release heat to the outside of the body, the heat is lost through evaporation. Because the body's ability to sweat, water vapor that appears on the surface of the skin through the pores of the skin can evaporate, by which the amount of heat released to the outside of the body.

In addition to the heat loss from the path of convective and evaporative from the skin, a type of heat loss occurs from the lungs through respiration because the air is out of the lungs usually colder and drier than on the surface of the lungs. Through the process of respiration the body losses heat that can reach 10% of the total heat produced by the body.

For your body stable, heat lost must be balanced with the heat produced. Otherwise, the heat content of the body will change, which causes the body temperature rises or falls. So if the heat production through he metabolic rate is higher than the sum of all heat lost, the stored heat will be marked positive (surplus), which means that the heat content of the body increases and body temperature will rise. If the stored heat is marked negative (deficit), heat loss is greater than the heat produced. The body becomes cold, and body temperature will fall.

REFERENCES

1. Anonim, 2005. Biophysics. Microsoft® Encarta® 2006 [DVD]. Redmond, WA: Microsoft Corporation.
2. Anonim. 2007. Description of Biophysics. Springer. European Biophysics Journal, [cited 2007 Feb 5]. Available at: URL: http://www.springer.com/
3. Blazejczyk, K. 2000. Assessment of Recreational Potential of Bioclimatic Based on The Human Heat Balance. Institute of Geography and Spatial Organization. Warsaw, Poland.
4. Brake, R and Bates, G. 2002. A Valid Methods for Comparing Rational and Empirical Heat Stress Indices. School of Public Health, Curtin University, Perth, Australia. Ann.Occup.Hyg. 46(2):165-174, [cited 2007 Mar.5]. Available from: URL: http://annhyg.oxfordjournals.org/.
5. Campbell, G. S. 1977. An Introduction to Environmental Biophysics. New York: Springers-Verlag.
6. Corlett, E. N. and Clark, T. S. 1995. The Ergonomics of Workspaces and Machines. A Design Manual. Taylor & Francis, 2nd erds. USA.
7. Epstein, Y and Moran, D. S. 2006. Thermal Comfort and the Heat Stress Indices. Industrial Health: 44, 388–398.
8. Havenith, G. 2004. Clothing Heat Exchange Models for Research and Application. Environmental Ergonomics Research Group, dept.Human Sciences, Loughborough, UK. p.66-73., [cited 2007 Apr 19]. Available from: URL: http://magpie.lboro.ac.uk/.
9. Havenith, G. 2002. The Interaction of Clothing and Thermoregulation. Human Thermal Environments Laboratory. Department of Human Sciences. Loughborough Univ., UK, [cited 2007 Apr 15]. Available from: URL: http://www.lboro.ac.uk/.
10. Havenith, G. 2001. Individualized Model of Human Thermoregulation for the Simulation of heat stress response. Human Thermal Environment Laboratory, Loughborough University. J Appl. Physiol., 90:1943-1954, [cited 2007 Mar 5]. Available from: URL: http://jap.physiology.org/.
11. Havenith, G. 1999. Heat Balance when Wearing Protective Clothing. Human Thermal Environment Laboratory, Loughborough University. Ann.Occup.Hyg, 43(5):289-296, [cited 2007 Mar 5]. Available from: URL: http://annhuy.oxfordjournals.org/.
12. Monteith, J. L. and Unsworth, H. M. 1990. Principles of Environmental Physics. 2nd ed. London: Edward Arnold.

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