Order this information in Print

Order this information on CD-ROM

Download in PDF Format

     

Click here to make tpub.com your Home Page

Page Title: Ecological effects
Back | Up | Next

Click here for a printable version

Google


Web
www.tpub.com

Home


   
Information Categories
.... Administration
Advancement
Aerographer
Automotive
Aviation
Combat
Construction
Diving
Draftsman
Engineering
Electronics
Food and Cooking
Math
Medical
Music
Nuclear Fundamentals
Photography
Religion
USMC
   
Products
  Educational CD-ROM's
Printed Manuals
Downloadable Books
   

 

reproductive organs, pancreatic islets, muscle, kidney, liver, and bone. Excretion
of zinc is mainly though the gastrointestinal tract, though some of the zinc is
reabsorbed. It is also excreted via urine, feces, sweat, hair, and saliva. Placental
transfer of zinc may also occur. The half-life of zinc in humans in 200 to
400 days.
Ecological effects
Zinc is an essential micronutrient for all living organisms. Because zinc is
essential, zinc is bioaccumulated by all organisms. The toxicity of zinc is
dependent upon its chemical form and degree of interconversion among the
various forms. Zinc will not be sorbed or bound unless it is dissolved, but bound
zinc will dissolve in the digestive tract following the ingestion of particulates.
The toxicity of undissolved zinc to a particular species depends on the feeding
habits. Aquatic plants and most fish are relatively unaffected by suspended zinc
in the water column. Both terrestrial and aquatic invertebrates and filter feeder
fish might be adversely affected by ingestion of sufficient quantities of
particulates containing zinc. The acute toxicity of zinc to aquatic animals is
influenced by several parameters including increasing hardness, abundant
dissolved oxygen, and low temperatures which lower the potential toxicity of
zinc.
Reported acute toxicity testing for freshwater organisms indicates that insects
are most resistant whereas cladocerans and the striped bass are the most sensitive
to zinc. The reported mean genus acute value for cladoceran is 50.56 ug/l at a
hardness of 50 mg/l. The final acute value representing zinc toxicity to
freshwater species is 108.4 ug/l at a hardness of 50 mg/l.
The range of species mean acute values for saltwater invertebrates extends
from 166 ug/l for embryos of the quahog clams, Mercenaria mercenaria, to
320,400 ug/l for adults of the clam, Macoma balthica. In general, early life stages
of saltwater invertebrates and fish are more sensitive to zinc than juveniles and
adults. The saltwater final acute value for zinc is 174.5 ug/l which is higher than
the acute value of 166 ug/l for the quahog clam. Chronic toxicity values range
from 47 to 852 ug/l and appear to be relatively unaffected by hardness.
Zinc was found to accumulate in freshwater animal tissues from 51 to
1,130 times the concentration present in the water (USEPA 1980). Steady-state
zinc bioconcentration factors for 12 aquatic species range from approximately
4 to 24,000 (USEPA 1980).
Zinc bioconcentration from soil by terrestrial plants, invertebrates, and
mammals, in values of 0.4, 8 and 0.6, have been reported. It has also been
reported that phytotoxic tissue zinc levels ranging from 200 to 400 ppm. Studies
have reported that 60 to 81 ppm of zinc in wheat and corn tissue is phytotoxic.
The tolerance of domestic livestock to zinc in animal feed ranges from 300 to
1,000 ppm (National Academy of Science (NAS) 1980). Zinc poisoning has
occurred in cattle. In one outbreak, poisoning was caused by food accidentally
contaminated with zinc at a concentration of 20 g/kg. An estimated intake of
D73
Appendix D Toxicological Profiles

Privacy Statement - Press Release - Copyright Information. - Contact Us - Support Integrated Publishing

Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business