Unit 4 Flashcards
(36 cards)
Toxicology
the study of poisons/toxins and their effects on organisms toxins can by either synthetic (human made) or natural
Environmental (Eco)Toxicology
includes toxicology as well as the additional investigation of the environmental factors influencing exposure dynamics
Toxins and Pest Management
- One of the most common uses of toxins and a basis for ecotoxicological studies is in the development, testing, and use of pesticides.
- Pesticides are used to protect crops plants, livestock, domestic animals and humans from damage and disease caused by microorganisms, fungi, insects, rodents and other “pests” and remove competitor plant “weeds” from crops.
- Can target a group of pests but not a specific kind of pest (for example target insects but bees effected)
pest
it is an undesirable competitor, parasite, or predator that interferes in some way with human welfare or activities
Persistence
- How long does a chemical such as a pesticide take to break down in the environment
- There is more opportunity for a chemical to interact in an ecosystem and disrupt biota when it sticks around for extended times
- Persistence should not last long, some improvement on this
Solubility
The ability of a chemical to dissolve in liquid
Water-soluble
- can be excreted from your body
- However, water soluble chemicals may easily enter and accumulate in aquatic ecosystems
Fat-soluble
- chemicals are absorbed into fatty tissues and there is potential of build up in bodies
- Readily transfer across cell membranes
- Worse kinds of toxins, hard to regulate and get rid of
Bioaccumulation and Biomagnification
Build-up of persistent fat-soluble chemicals in the body over time
Biological Magnification of the toxin in the food-web
- Bioaccumulation leads to concentration (or build up) in each trophic level based on feeding relationships in a food web
- Animals higher on the food chain accumulate far more toxins than those lower on the food chain
- Top predators exhibit unsafe concentrations in their tissues
Acute Exposure
- Symptoms develop rapidly following exposure and absorption
- Usually includes exposure to large amounts of a chemical
- Usually results in death
Chronic Exposure
- Takes place over a long period of time following prolonged exposure to often low-levels of pollutants
e. g. smoking development of lung cancer
Antagonistic Effect
these are chemicals that interact to cancel out or lessen the toxicity effect
Synergistic Effect
combining these toxins results in a pronounced effect and much greater response than would be expected
Mobility of Toxicants
The intended pathway of broadcast spraying a chemical differs from the actual pathway(s) it takes in the ecosystem:
-Low % reaches target
-About 98% can end up in air surface water, groundwater, bottom sediments
Local mobility-areas around on the site of toxic exposure are affected as well
Mobility and Long Range Transport of (Air) Pollutants (LRTAP)
- Grasshopper Effect because pollutants leap towards poles with (convective) air currents
- Substances are transported by wind and water and eventually deposit hundreds of thousands of kms from source
- Convection pushes these chemicals up to the arctic (to the poles) and affecting their food webs and ecosystems
Food-Web Dynamics Impacting Non-Target Organisms
Broadcast spraying – crop dusting aircraft or tractor-drawn sprayers are often used, resulting in the exposure of many non-target species to the spray
indirect ecotoxicological stresses
Toxics that are purposely released may cause changes to habitat
- For example, herbicides kill plants and thereby change the habitat of animals, depriving herbivores of their preferred foods
- Predators may be killed by pesticide drift and indirect exposure. Without the predator, the pest is more rapidly able to rebound and its carrying capacity much larger
Genetic Based Tolerance
- Over successive applications of the pesticide, the mutant survives and contributes to the new population
- Overall resistance develops as the mutant gene dominates in the population
- Higher concentrations and/or new pesticides are required to affect the mutant population.
- Through repeated application of pesticides we encourage the mutant to be the dominant in the population, therefore they are no longer resistant to the pesticide
How Do We Manage Toxins?
Scientists will conduct risk assessments in which they describe and quantify the hazards and evaluate the probability of harm through determination of the risk.
Risk
the probability that an activity or exposure to a substance will be harmful
Risk Assessment
- Hazard identification (identify and describe the hazard)
- Dose-response assessment (information on the toxicity studied in the lab and the causes of the toxin)
- Exposure assessment (evaluate what the toxin will look like out in the environment)
- Risk characterization
Dose
amount that enters the body
Response
type & amount of damage
