Situation A new mining process is being considered in which a chemical is used to more efficiently extract the mined metal. The process requires the limited release of a chemical into the environment. What is the risk of this chemical on freshwater fish in ponds and lakes?
Steps: Tier 1: Hazard ID The chemical is a neurotoxin and is toxic to fathead minnow and bluegill sunfish in test systems.
Dose-response Data The LC50 for minnow is 1.2 micrograms/liter. The NOEC (No Observed Effect Concentration) is 0.1 micrograms/liter.
Residue/Exposure Analysis Assumptions: a worst-case scenario involves release of the chemical on a highly erosive and very steep upland slope, with heavy rainfall occurring very soon after. Ten acres of surface area, the entire area of the release, uniformly high slopes, runoff drains directly into a six-foot deep, oneacre pond. Release rate = the highest rate being evaluated.
Data used in the environmental modeling of the chemical (you donât need these data for the questions; look up the terms âaerobic half-life, Koc, photolysis, solubilityâ if you are not familiar with them):
Application rate: 5 lbs. of the chemical per acre
soil aerobic half-life = 30 d
Koc = 6,000
photolysis = 7 d
solubility = 2
aquatic aerobic metabolic half-life = 7 d
The modeling results indicate that (you need these values for the questions): Acute exposure (EEC peak value) = 10.7 micrograms/liter Chronic exposure (EEC 21-day value) = 3 micrograms/liter
Questions to Answer (Show Work)
a. What is the acute risk quotient (Exposure ÷ Effect, LC50)?
b. What is the chronic risk quotient (Exposure ÷ Effect, NOEC)?
c. The following are the EPA Levels of Concern (LOC's) (expressed as risk quotients). How do your calculated risk quotients compare to the LOC's (2 points)? - Non-endangered species Acute RQ should be ⤠0.5; - Endangered species Acute RQ should be ⤠0.05 - Non-endangered and endangered Chronic RQ should be ⤠1.0
d. What data elements and exposure refinements are needed for higher-tiered assessments?
Situation A new mining process is being considered in which a chemical is used to more efficiently extract the mined metal. The process requires the limited release of a chemical into the environment. What is the risk of this chemical on freshwater fish in ponds and lakes?
Steps: Tier 1: Hazard ID The chemical is a neurotoxin and is toxic to fathead minnow and bluegill sunfish in test systems.
Dose-response Data The LC50 for minnow is 1.2 micrograms/liter. The NOEC (No Observed Effect Concentration) is 0.1 micrograms/liter.
Residue/Exposure Analysis Assumptions: a worst-case scenario involves release of the chemical on a highly erosive and very steep upland slope, with heavy rainfall occurring very soon after. Ten acres of surface area, the entire area of the release, uniformly high slopes, runoff drains directly into a six-foot deep, oneacre pond. Release rate = the highest rate being evaluated.
Data used in the environmental modeling of the chemical (you donât need these data for the questions; look up the terms âaerobic half-life, Koc, photolysis, solubilityâ if you are not familiar with them):
Application rate: 5 lbs. of the chemical per acre
soil aerobic half-life = 30 d
Koc = 6,000
photolysis = 7 d
solubility = 2
aquatic aerobic metabolic half-life = 7 d
The modeling results indicate that (you need these values for the questions): Acute exposure (EEC peak value) = 10.7 micrograms/liter Chronic exposure (EEC 21-day value) = 3 micrograms/liter
Questions to Answer (Show Work)
a. What is the acute risk quotient (Exposure ÷ Effect, LC50)?
b. What is the chronic risk quotient (Exposure ÷ Effect, NOEC)?
c. The following are the EPA Levels of Concern (LOC's) (expressed as risk quotients). How do your calculated risk quotients compare to the LOC's (2 points)? - Non-endangered species Acute RQ should be ⤠0.5; - Endangered species Acute RQ should be ⤠0.05 - Non-endangered and endangered Chronic RQ should be ⤠1.0
d. What data elements and exposure refinements are needed for higher-tiered assessments?
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