Glossary
Acute toxicity
The adverse effects of a substance that result from a single exposure or from multiple exposures in a short period of time (usually less than 24 hours).
Example:
Ingesting a large amount of a cleaning product causing immediate nausea and vomiting is an example of acute toxicity.
Chronic toxicity
The adverse effects resulting from long-term or repeated exposure to a substance, often over a significant portion of an organism's lifespan.
Example:
Developing cancer years after prolonged exposure to a low level of a carcinogen is an example of chronic toxicity.
EC50 (Effective Concentration 50)
The concentration of a substance that produces a specific non-lethal effect in 50% of the population, typically used for environmental exposures.
Example:
An ecotoxicologist might determine the EC50 of a chemical on algae growth, finding the concentration that inhibits 50% of their growth.
ED50 (Effective Dose 50)
The dose of a substance that produces a specific non-lethal effect in 50% of the test population.
Example:
For a pain reliever, the ED50 might be the dose at which 50% of patients report significant pain reduction.
LC50 (Lethal Concentration 50)
The concentration of a substance in air or water that kills 50% of a test population, used for environmental exposures rather than direct doses.
Example:
Aquatic scientists might determine the LC50 of an oil spill component in water to understand how much of it would kill half of a fish population in a given time.
LD100 (Lethal Dose 100)
The dose of a substance that is lethal to 100% of the test population.
Example:
If a certain venom has an LD100 of 0.1 mg/kg, it means that any individual exposed to that dose or higher will certainly die.
LD50 (Lethal Dose 50)
The amount of a substance (typically in mg/kg of body weight) that kills 50% of a test population of animals. It serves as a benchmark for a substance's acute toxicity.
Example:
If a new pesticide has an LD50 of 10 mg/kg, it means that a dose of 10 milligrams per kilogram of body weight is expected to be lethal to half of the test subjects.
LDlo (Lowest Dose Lethal)
The lowest dose of a substance that has been observed to cause death in any individual of a test population.
Example:
Even if the LD50 for a chemical is high, finding an LDlo of just 1 mg/kg in a sensitive species would still raise significant safety concerns.
NOAEL (No-Observed-Adverse-Effect Level)
The highest dose of a substance at which no adverse (harmful) effects are observed in a test population.
Example:
Regulators aim to set human exposure limits well below the NOAEL determined in animal studies to ensure a wide margin of safety.
NOEL (No-Observed-Effect Level)
The highest dose of a substance at which no observable effects (adverse or otherwise) are detected in a test population.
Example:
A study might find a NOEL for a food additive, meaning below this dose, no physiological changes are detectable.
POD (Probable-Effect-Dose)
The dose at which a specific effect is likely to occur in a population.
Example:
In toxicology, researchers might identify a POD for a certain pollutant, indicating the dose at which a particular health outcome becomes probable.
Relative toxicity
A comparison of the harmfulness of different substances, often determined by metrics like LD50 or LC50, where a lower value indicates greater toxicity.
Example:
Comparing the relative toxicity of two different herbicides, one with an LD50 of 50 mg/kg and another with 500 mg/kg, shows the first is significantly more dangerous.
Route of exposure
The pathway by which a substance enters the body, such as oral (ingestion), dermal (skin contact), or inhalation (breathing).
Example:
Understanding the primary route of exposure for a chemical, like whether it's absorbed through the skin or inhaled, is crucial for designing appropriate safety gear.
TD50 (Therapeutic Dose 50)
The dose of a substance that produces a desired therapeutic effect in 50% of the population.
Example:
Pharmaceutical companies determine the TD50 of a new drug to understand its efficacy in treating a condition.