f nvironment constitutes the non-living (air, Lwater, land, energy etc.) as well as the living (biological and social) systems surrounding man. Environmental biochemistry primarily deals with the metabolic (biochemical) responses and adaptations in man (or other organisms) due to the environmental factors. A healthy environment is required for a healthy life which is however, not really possible or practicable. This is mainly because of the atmospheric (climatic) changes and environmental pollution. Environmental biochemistry is a very vast subject. The basic concepts regarding the atmospheric changes and environmental oollution on humans are dealt with here. The climatic changes include cold, heat etc. . The body makes every effort to maintain its normal temperature (despite cold and surroundings) for optimal physiological biochemical functions. EXPOSURE TO COLD Short-term exposure to cold causes shivering (mainly due to skeletal muscle) to produce extra heat. Heat is generated by the hydrolysis of ATP' tw,+. g,,:t:t; j,i+'r e "t: 94 r:li:*s;ie Chronic exposure to cold results in non- shivering phase which is characterized by several metabol ic adaPtations. heat and Energy metabolism : Heat generation by a process called chemical thermogenesis occurs in non-shivering phase. The foodstuffs undergo oxidation to generate heat at the expense of growth and other anabolic processes. Elevation in BMR, and increased intake oi foods are observed. Lipid metabolism : Stored fat (triacylglycerol) in the adipose tissue is mobilized to supplyfree fatty acids for oxidation and production of energy. Brown edipose tissue, particularly in neonatal life, significantly contributes to thermogenesis. . Hormonal changes : Thyroxine, a hormone closely associated with energy metabolism, is elevated. Further, corticosteroids are increased on exoosure to cold. EXPOSURE TO HEAT There is a continuous generation of heat by the body due to the ongoing biochemical processes, referred to as metabolic heat. This heat has to be exchanged with the environment to maintain a constant body temperature. On exposure to heat in surroundings, as happens in sLrmmer, the body is subjected to an uncomfortable situation (since temperature of the surroundings is much higher than that of the body). However, heat is still lost from the body through sweating and evaporation. Normally, the body (thermoregulation) gets acclimatized to higher temperature within 3-5 days. Heat stroke : lt is characterized by the failure of the heat regulatory system (thermoregulation) of the body. The manifestations of heat stroke include high body temperature, convulsions, partial (some times total) loss of consciousness. In extreme cases, heat stroke may cause irreversible damage to brain. The treatment for the heat stroke involves rapid cooling of the body. The milder form of heat stroke is referred to as heat syncope. Although the body temperature is not raised much in this condition, the blood pressure falls and the person may collapse suddenly. Heat syncope is easily reversible. Environmental pollution may be regarded as the addition of extraneous (foreign) materials to air, water or land which adversely affects the quality of life. Pollution may be caused by physical, chemical or biological processes. The term pollutant refers to a substance which increases in quantity due to human activity and adversely affects the environment (e.9. carbon monoxide, sulfur dioxide, lead). A substance which is not present in nature but released during human activity is the contaminant (e.g. methyl isocyanate, DDT, malathion). A contaminant however, is regarded as a pollutant when it exerts detrimental effects. Environmental pollution may be considered in different ways-industrial pollution; agricultural pollution; pollution due to gaseous wastes, liquid wastes and solid wastes.