Environmental Toxicology and exploring ATSDR toxicological profiles MSC-210 Marine Environmental Sampling & Analysis Lecture 8
Toxicology Definitions Environmental Toxicology: The study of the fate and effects of contaminants in the environment Environmental Health Toxicology: The study of the adverse effects of environmental contaminants on human health Ecotoxicology: The study of the adverse effects of environmental contaminants on ecosystems and constituents 2 November 2015 CFCC MSC-210
Environmental Health Toxicology vs Ecotoxicology Environmental Health Toxicology Ecotoxicology Protects humans Humans separated from environment; rarely includes non-living environment Primarily relies on animal studies to infer hazards for humans Protects populations and communities of different species Inclusive of species and the non-living environment Experimentation generally conducted on the actual species of concern 3
Environmental Contaminants Persistent Bioaccumulate Toxic 4
Why won t you go away? Environmental Persistence: Defined as how long a chemical will be in a given form Determined by degradation processes Described in terms of half-lives Half-life The half-life, t 1/2, is the amount of time needed for a chemical s concentration to decrease by half compared to its initial concentration. Its application is used in chemistry and medicine to predict the concentration of a substance over time. 5
Environmental Persistence Contaminant Half-life (days) Media DDT 3,650 Soil TCDD 3,285 Soil Atrazine 750 Water Benzoperylene 420 Soil Phenanthrene 138 Soil Carbofuran 45 Water 6 November 2015 CFCC MSC-210
Why won t you go away? Bioaccumulation: Process by which organisms accumulate chemicals Can occur directly or indirectly Primary sites of uptake: Lungs Gills GI tract Skin 7
Bioaccumulation in the Aquatic Environment Major site for chemical transition from abiotic environment to biota Aquatic environment serves as a: Transport medium Contaminant sink Habitat for organisms with gills 8
Bioaccumulation Factors (BAFs) The ratio of the chemical concentration inside an organism to the water concentration at equilibrium BAF = C organism C water Chemical BAFs DDT 127 000 TCDD 39 000 Endrin 6 800 Pentachlorobenzene 5 000 Leptophos 750 Trichlorobenzene 183 9
Trophic Transfer: Biomagnification (Bioconcentration) DDT 0.000003 ppm in water 0.04 ppm in zooplankton 0.5 ppm in small fishes 2 ppm in large fish 25 ppm in predatory birds 11
Delayed Toxicity Bioaccumulating toxicants are lipophilic May be stored in fat deposits & mobilized at a later time when it will elicit effects Food Shortage or Hibernation Preparations for Reproduction Transference to Offspring 12
Factors Affecting Bioaccumulation Chemical persistence Chemical lipophilicity Organism s metabolism Organism s elimination capabilities 13
Toxicity Classification & Registration
Acute Toxicity: Immediate toxicity elicited in response to short-term exposure Typically associated to an accidental release or improper usage Acute vs Chronic Toxicity And related quantifications Commonly quantified as: LD 50 LC 50 15
Chronic Toxicity: Toxicity elicited following long-term exposure Commonly assessed using sub-lethal endpoints Also could be cumulative lethality Acute vs Chronic Toxicity And related quantifications Commonly quantified as: NOAEL LOAEL Chronic Value Acute to Chronic Ratio (ACR) 16
Globally Harmonized System for the Classification & Labeling of Chemicals and Hazards
Let s explore how toxicity is discussed by the ATSDR By Congressional mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) produces "toxicological profiles" for hazardous substances found at National Priorities List (NPL) sites. These hazardous substances are ranked based on: Frequency of occurrence at NPL sites Toxicity Potential for human exposure Toxicological profiles are developed from a priority list of 275 substances. ATSDR also prepares toxicological profiles for the Department of Defense (DOD) and the Department of Energy (DOE) on substances related to federal sites.
Let s explore how toxicity is discussed by the ATSDR Toxicological profiles are developed in two stages: (1) DRAFTS: o The toxicological profiles are first produced as drafts. o ATSDR announces in the Federal Register (FR) the release of these draft profiles for a 90 day public comment period. (2) FINALS: o After the 90 day comment period, ATSDR considers incorporating all comments into the documents. o ATSDR finalizes the profiles. ATSDR Website
References Lecture Content Graham, S., Hofelt, C., and LeBlanc, C. (2013). NCSU lecture Environmental Toxicology. Nov 19, 2013. North Carolina State University. U.S. EPA. (2000). Bioaccumulation Testing and Interpretation for the Purpose of Sediment Quality Assessment Status & Needs. U.S. Environmental Protection Agency, Office of Water (4305) and Office of Solid Waste (5307W). EPA Document 823-R-00-001. February 2000. Images Slide 2: Toxicology https://www.gravitywerks.com Slides 5 & 7: Fish Cartoons https://www.michigan.gov Slide 8: Gills https://www.britannica.com Slide 16: GHS https://www.osha.gov 20