Stephen Vantassel here wildlife control consultant. Wanted
to talk today about L.D. 50 and understanding LD 50 as motive. Many of you know
I’m involved in vertebrate control so the role of pesticides to control
vertebrates raises a lot of issues and concerns about the relative toxicity of
some of these toxic loans fume against that are being used to control unwanted
pest vertebrates. So let’s back up a little bit and talk about the relationship
between notions of risk and harm.
Now on another podcast I would kind of been deep in the
notion of risk here, I’m not gonna go as far deep into that as before but I do
want to give you concept to help you understand the difference between
understanding risk and understanding what harm is. Because these are two
different concepts. Risk is the probability or the potential for a negative
event or the probability of harm that something bad is going to happen harm.
The concept of harm is what is the actual effect of that negative
event so risk is the potential.
The likelihood that something bad is going to happen harm is
it is an analysis or discussion of what that actual negative event actually is.
So when we’re talking about LD 50. We really focusing in we’re drilling down on
this notion of harm. What is this. What is the harmful
Effects of this particular toxic and or fumigate or many of
your cases because many of you deal with bugs of this particular pesticide. So
let’s kind of drill into that a little bit now if you’re heard by other podcast
you would have heard me talk about how hazard or risk is exposure times
toxicity.
And so we’re going to be focusing not on the exposures side
but we’re going to be focusing on the toxicity side. That’s that that harm
element of this particular toxicity. How lethal is this particular element. And
even under toxicity we have to be breaking it down a little bit more. Our focus
is going to be on its lethality not the toxicity in terms of its persistence.
That’s a different question. We’re looking at the acute effects of the problem
not the long term effects. Now acute effects are typically defined in pesticide
use as what the effect of a pesticide is that occurs within twenty four hours
Long. The long term effects are beyond 24 hours in some
cases some pesticides may have effects for years. But when we’re dealing with
LV 50s we’re looking at acute toxic effects. All right so let’s kind of talk
about
Understanding relative toxicity. Now L.D. 50 which stands
for Lethal Dose 50 percent it’s symbolized as capital L capital D with a
subscript number of 50 Five 0. That’s typically how it sits it’s so we call it
L.D. 50 Lethal Dose 50 percent. Now what it is it’s a a formulaic way to give a
number to how potentially lethal this particular product is and it’s often
given in the sense of milligrams per kilogram. How much is needed to kill 50
percent of the test subject. So if you have 20 animals how many how much of the
dose at a 50 milligram per kilogram rate do you need to kill 50 percent of those
animals which would be in this case 10 so let’s talk about milligrams and kg so
a milligram is one millionth Of a kilogram. Now if you’re trying to we know
we’re not we don’t really use metric much in the United States but I think
that’s probably changing over time.