down stream from a sewage-treatment plant. Because there is almost always a risk of exposure to sharp objects or water-borne diseases during collection of benthic samples, gloves and waders should be worn when these samples are collected and processed. Appro priate vaccinations against water-borne diseases should be considered when there is likelihood that such diseases could be present. Safety glasses or goggles are another consideration when personnel are working in contaminated situations and handling fix atives or preservatives. The mouth should be kept closed or covered during sample collection and processing to avoid accidental ingestion of contaminated water, sediment, or detritus. A sample or sample site is always assumed to be highly contaminated. PFD's are mandatory when working conditions involve swift or deep water. When chestwaders are used, the suspenders are worn on the outside of all clothing, including PFD's, so that the waders can be removed in an emergency, such as accidentally falling into deep or swift water. Wearing a belt around the top of chestwaders is discouraged because this complicates removal of waders in an emergency situation, and air trapped below the waist provides excessive buoyancy that interferes with the correct funct ioning of the PFD.
Preservation of invertebrate samples in the field involves the use of a 10-percent solution of buffered formalin. This material is a suspected carcinogen (U.S. Environmental Protection Agency, 1981) and should be handled only in well ventilated areas while wearing gloves and eye protection. Parts of the body that come in contact with formalin should be flushed with large amounts of water. If the eyes are involved, they should be flushed with plenty of water, and the injured person should receive medical treatment as soon as possible. A suitable eye-wash solution (for example, sterile deionized water) should be available during field work. Formalin should be purchased as 10-percent buffered formalin. The acquisition, storage, and transportation of full-strength formalin (37-percent formaldehyde) is discouraged. Formalin and formalin-preserved samples should not be transported in the passenger compartment of vehicles because of the risk of exposure if a container breaks or leaks. Instead, formalin and formalin-preserved samples should be transported in the back of pick-up trucks, in roof-top carriers, or in other areas where leaking formalin cannot endanger human health. Any waste formalin is disposed of as hazardous waste according to local, State, and Federal guidelines.
Field sampling also involves a number of environmental risks stemming from contact with the local flora and fauna. Field personnel should be instructed on how to recognize and avoid poisonous plants, snakes, and insects. Contact with poisonous plants ty pically occurs near streambanks and can best be avoided by inspecting the bank and keeping away from any suspect plants. Snakes and venomous insects are often found around trees and snags that overhang or protrude from the river bank. Such locations sho uld be approached from downstream and examined at a distance to determine if snakes, wasps, or bees are present. If a snake is present, it may be encouraged to leave by shouting, throwing small stones, or disturbing the tree that it occupies. However, if an active wasp nest or bee hive is observed, it should not be disturbed and an alternative sampling location should be chosen. If someone is thought to have been bitten by a poisonous snake, it is generally better to transport the individual immediatel y to the nearest hospital or doctor for treatment rather than applying treatment in the field prior to transport to a medical facility. Likewise, if someone is stung by a bee or wasp, that person should be observed and taken to a hospital at