overboard  and  become  lost  at  sea.  Drug  abuse  or permanent  and  temporary;  headaches;  fatigue;  and dependence is not only hazardous to the abuser, but also to other personnel, to equipment, and to the operational readiness of the command. Polydrugs have created still another dimension of drug abuse. The term refers to the mixing of two or more drugs. Mixing alcohol with another drug is the most common  form  of  polydrug  abuse.  This  combination produces  effects  that  can  be  fatal. FATIGUE Fatigue begins when a person starts a task; the fatigue increases as the task continues. It decreases awareness  and  reflex  actions  while  increasing  the chance  of  error.  Symptoms  include  lower  quality  of performance,  irritability,  impatience,  forgetfulness, confusion, and increased errors. Hard work long hours, and lack of sleep produce fatigue. In addition, such stresses  as  vibration,  heat,  high  or  constant  noise, inadequate  illumination,  anxiety,  boredom,  monotony, and change in routine can produce fatigue. MOTION  SICKNESS Since motion sickness produces severe nausea, it can weaken, distract, or disorient people. The most commonly experienced forms stem from the motions associated with aircraft, cars, trains, and ships. This illness is particularly dangerous because it causes a loss in  normal  alertness  and  decision-making  abilities.  Such a loss can cause a person to make serious mistakes. Once the body becomes adjusted to these movements, through training  and  adaptation,  nausea  disappears  and  normal functioning returns. EXTREME  TEMPERATURES Extreme temperatures impair a person’s overall performance,    which   increases   the   chances   of inefficiency and mishaps. Heat stress and temperature extremes cause problems such as fatigue, increased reaction time, decreased mental awareness, and loss of dexterity  and  coordination. nausea. Each of these effects can impair performance. VIBRATION We  often  overlook  vibration  as  a  potential  source  of decreased  work  performance,  and  yet  it  routinely accompanies  many  activities.  Very  low-frequency, high-amplitude  vibrations  can  cause  motion  sickness. Prolonged exposure to vibration commonly produces annoyance and fatigue, which can reduce performance and  effectiveness.  Exposure  to  levels  of  vibration  that produce  discomfort  can  induce  permanent  physical damage to the internal organs. VISUAL ACUITY Mishap-free  performance  requires  good  visual acuity.  Different  problems  can  affect  your  vision  during the day and at night. The most common problem during daylight is glare. Intense light reflected in random directions  causes  glare.  Glare  is  hazardous  because  it can  momentarily  blind  you.  The  blindness  can  continue for hours until your eyes have had time to adjust to low levels of light. Even if your eyes adjust easily, your visual acuity at night is not as good as it is during the day. Night vision is  extremely  sensitive  to  stray  light  sources.  When  your eyes have adapted to darkness, a sudden flash of light can blind you, as glare does during the day. These conditions increase the chances of mishaps. MENTAL FACTORS Mental factors have been cited as causes involved in  numerous  mishaps.  Mental  factors  range  from  just being in a bad mood to having a serious personality disorder.   Although   medical   professionals   usually investigate mental factors, all mishap investigators should  look  at  these  factors.  In  serious  mishaps,  a medical  officer  is  assigned  to  determine  physical  and mental  causes  of  human  error.  Medical  records,  prior injuries,   responses   to   stress,   and   documented personality  disorders  are  reviewed  and  investigated. NOISE BEHAVIORAL FACTORS Unnecessary  or  unpleasant  noise  causes  stress  by Behavioral   factors   include   actions   such   as overloading  a  person’s  nervous  system.  Stress  can  bring skylarking,   risk-taking,   showing   off,   inattention, about  emotional  outbursts.  Since  emotional  outbursts disregarding  instructions  or  orders,  and  flaunting are  impulsive  and  unrestrained,  they  can  result  in authority.  Such  behavior  results  when  personnel  ignore mishaps. Intense noise can cause hearing loss, both safe  work  procedures  because  of  undesirable  motives. 3-3