ABSTRACT
Human waste and sewage are the main sources of biological contaminants, although contaminants can arise from commercial and industrial sites. Many inland lakes have become contaminated by agricultural herbicide and fertilizer runoff. Toxins are substances produced by microorganisms, plants, or animals that cause illness in people. They work their insidious effects by interfering with tissue and cell functions. Pathogens are infectious agents that can cause disease in people. Viruses are the smallest of the pathogens that are able to reproduce, but they are incapable of independent existence. Commercial divers use helmets exclusively for diving in any water that carries with it the possible threat of contamination. The common watery depositories used by criminals have characteristics that make them attractive. In March 1999, a call was placed to the Stradford, Texas, sheriff’s office regarding a missing person. Neighbors had not seen the young Hispanic woman or the man she lived with for over 43 days.
