drink   commercially   prepared   electrolyte supplements in place of water. Do NOT take salt tablets unless specified by medical personnel. Do NOT drink alcoholic beverages, because alcohol depletes the level of fluids in the body. Remember,  the  effects  of  heat  stress  are  cumulative (add up). Once you have heat cramps, heat exhaustion, or heatstroke, you are twice as likely to experience a heat stress-related  incident;  your  body  has  an  increased sensitivity  to  heat.  Your  awareness  of  the  factors  that contribute to heat stress and their prevention, as well as your strict adherence to established exposure limits, will help prevent your becoming a victim of heat stress. POLLUTION Before  understanding  how  pollution  affects  you personally,  you  must  take  a  realistic  look  at  pollution. Pollutants,  whether  airborne  or  waterborne,  adversely affect  the  food  chain  and  often  are  directly  harmful  to humans. As Navy personnel, our primary concern is to control  the  pollutants  aboard  ship  to  minimize  the pollution risk to ourselves and the environment. OIL  AND  CHEMICAL  POLLUTION Fuel oil and chemical cleaning solvents are often used aboard Navy ships, and the possibility exists for a spill. These pollutants collect in the ship’s bilges. From the ship’s bilges, the pollutants are pumped into a waste oil  collecting  can. Oily wastes behave just as their definition suggests: an oily waste is any solid or liquid substance that, alone or in a solution, can produce a surface film or  sheen when it is discharged in clean water. Most oily wastes are   derived   (come)   from   petroleum   or   have characteristics of petroleum products. Waste oil is an oily waste that cannot be reused by the ship, and it contains  only  small  amounts  of  water.  Any  mixture  that causes a sludge or emulsion to be deposited beneath the surface  oil  and  chemical  pollution  of  the  water  is considered to be an oily waste. Oily wastes frequently present a shipboard pollution problem. (Refer to the  Naval  Ships’  Technical  Manual (NSTM),  chapter  593.)  Oily  wastes  derived  from lubricating oils are caused by tank cleaning operations, leakage and drainage from equipment and systems, stripping  from  contaminated  oil-settling  tanks,  and ballast  water  from  fuel  tanks  of  noncompensated  fuel systems  during  the  ship’s  defueling,  refueling,  or internal transfer operations. You  may  think  that  if  a  small  amount  of  oil  is pumped overboard, it cannot really cause much damage. Or can it? Remember, oil is less dense than water. It floats on the surface of the water and is carried by the action  of  winds  and  tides.  Oily  wastes  can  contain appreciable  amounts  of  volatile  petroleum  or  fuel products. When these wastes are confined in spaces, such  as  tanks  and  bilge  compartments,  they  become  a source  of  floating  flammables  or  vapors  that  are potentially  hazardous  to  personnel  and  equipment.  If these vapors collect in a confined area, such as a pocket underneath a pier, they could explode if exposed to an open flame, such as from a welding operation or from a spark from a grinding wheel. Remember, YOU might be the person who is operating the torch, welder, or grinding  wheel. Besides being harmful to the environment and to people, oil and chemical discharge is also against the law.  The  Oil  Pollution  Act  of  1961  prohibits  the discharge of oil and oily waste products into the sea within 50 miles (150 miles in some cases) of land. A more  recent  law,  the  Federal  Water  Pollution  Control Act of 1970, prohibits the discharge of oil by any person or agency from any vessel or facility into the navigable waters  of  the  United  States  inside  the  12-mile  limit.  All oil  spills  or  sheens  within  the  50-mile  prohibited  zone of  the  United  States  must  be  reported  immediately. Oil Spill Prevention Shipboard oil pollution is controlled by the efficient use of the oily waste control system that is incorporated into your ship. Oil pollution control systems reduce oily waste  generation,  store  waste  oil  and  oily  wastes, monitor oil and oily wastes, and transfer waste oil and oily  wastes  to  shore  facilities.  Effective  use  of  your ship’s  oil  pollution  control  system  depends  on  operators’ knowledge of the ship’s pollution abatement system. To use  your  ship’s  oil  pollution  control  system  effectively, operating personnel are trained and plans are made so that oil and oily waste are handled properly. Other requirements  for  your  ship  include  ensuring  that equipment  functions  properly  and  that  bilges  are  kept dry and free of oil. The minimum use of detergents is recommended when bilges and equipment are cleaned. Also,  always  give  proper  attention  to  preventive maintenance  requirements. The best prevention method any vessel can use against oil or chemical pollution is not to discharge pollutants into the sea. However, spills do occur during refueling operations. For example, to keep a ship “on an even keel,” fuel oil maybe transferred from one tank to 13-3