Picture of Janis Reed, Ph.D., BCE

Janis Reed, Ph.D., BCE

Technical Services Manager PCO Product Development

Post Date
Monday - July 31 - 2017
Post Title

What You Need To Know About Toxicity Ratings



How Much Makes it Lethal?

On SDSs or a toxicity report you may have come across a rating of toxicity, known as LD50 or LC50. These ratings are the value, in weight or concentration, it takes to kill 50% of the test animals in one dose within a set time.

LD50 means lethal dose, 50% of a population, and is usually shown in weight of the substance administered to weight of the test subject, usually in milligrams of toxic substance per kilogram of body weight.

LC50 means lethal concentration, 50% of a test population where the concentration is an amount of a toxic substance dissolved in water or as a gas in air it takes to kill 50% of a test population.

TEKKO Pro Safety Data Sheet
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LT50 is lethal time, 50% of a test population where the time is the amount of time a dose of a toxin takes to control 50% of a test population.

To determine LD50, groups of test animals, such as rats, are exposed to an ever-increasing amount of a toxic substance, or a dose. The test groups are then observed for mortality, or how many in the group die in a defined time. These data are then plotted on a graph and a mean, or average, LD50 is established. If half of the animals die at a very low dose, the LD50 will be low and if it takes a very high dose to kill half of the animals, the LD50 will be higher.

Which is More Toxic?

These values are often used as a general indicator of a substances toxicity, allowing us to compare substances based on their toxicity.
The rating of LD50, LC50, and LT50 are somewhat counter intuitive. The lower the value, the more toxic the pesticide.
Let’s look at some specific examples:
The LD50 value for common table salt is approximately 3000 mg/kg when administered orally. In comparison, the LD50 value for aspirin is 200 mg/kg when administered orally.

So, which common household substance, salt or aspirin, is more toxic?

In this case, aspirin is much more toxic than salt. In fact, the LD50 for aspirin is 10 times lower than standard table salt and therefore considerably more toxic of a substance.

Remember, the lower the LD50, the more toxic the substance.
In addition to providing the user with toxicological information, these values are one of the criteria used to determine signal words on a pesticide label. Typically, substances with very low LD50s are assigned a signal word of “Danger/Danger – Poison” and substances with very high LD50 values are assigned a signal word of caution or may carry no signal word at all.

Look up the SDS on the pesticide you use most often. What is the LD50? How does it compare to aspirin? You might be surprised.


 

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