Probit, probability unit as related to public deception campaigns, vaccines and other biological and chemical weapons.

Katherine Watt

Jan 27

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Orientation for new readers; American Domestic Bioterrorism Program; Tools for dismantling kill box anti-law

Working last week to track the development and use of specific result, potency and other key undefined and pseudo-defined terms from the 1902 Virus-Toxin law to the 1938 Food, Drug and Cosmetic Act, 1944 Public Health Service Act and beyond, I learned the word probit, and the terms probit line, probit slope, probit function and probit model.

The earliest terms applied by military-public health officers to give the false public impression that specific results or potency for viruses, serums, toxins and antitoxins can be observed, measured, defined and described, were immunity unit or antitoxin unit.

Both “units” were derived, by dilution and arbitrary assumptions, from the median minimum lethal dose of a toxic, heterogeneous, unstable mixture of foreign (xeno- or non-self) biological substances, when injected into a group of living test subjects such as guinea pigs, mice, rabbits and dogs.

Probit is a portmanteau of probability unit, coined by Chester Ittner Bliss in 1934.

Wikipedia:

“The idea of the probit function was published by Bliss in a 1934 article in Science on how to treat data such as the percentage of a pest killed by a pesticide. Bliss proposed transforming the percentage killed into a "probability unit" (or "probit").”

The terms probability unit and probit are related to biological product nomenclature such as immunity unit (in use by 1905); antitoxin unit (by 1909); international unit (by 1931); and international antitoxic unit (by 1946).

Probability unit is also related to toxicology and biological and chemical warfare nomenclature:

LD50 - median lethal dose, dose of a drug or microbe that will kill 50% of the subjects receiving it, expressed as mass of substance administered per unit mass of test subject, ie mg of substance per kg body mass);
ID50 - median infective dose, dose that has a 50% probability of producing a specified response to infection, considered as symptoms or signs of disease or death;
TCID50 - tissue culture median infective dose; dilution of a virus required to infect 50% of a given cell culture.
ED50 - median effective dose, dose of a drug or microbe that has a 50% probability of producing any precisely definable effect;
Ct50 - measure of intensity of exposure; function of concentration and time, not of dose that actually penetrates the body; concentration applies as much to pathogens as to chemical agents; if concentration (C) is expressed in mg-m³ and time (t) is in minutes, the Ct is mg-min/m³
LCt50 (median lethal exposure intensity; function of concentration and time).

The related quantities LD₅₀/30 or LD₅₀/60 are used to refer to a dose that will be lethal to 50% of the dosed population within (respectively) 30 or 60 days.

One of the source documents is a 1970 report by World Health Organization consultant, titled Health Aspects of Chemical and Biological Weapons.

At. p. 85:

Specification of toxicity and infectivity
The LD50 (lethal dose 50) of a drug or a microbe is the dose that will kill 50% of the subjects receiving it.
It may also be defined as the dose that has a 50% probability of killing any particular individual. Correspondingly, and more generally, one can specify an ED50 (effective dose 50) as the dose that has a 50% probability of producing any precisely definable effect, for infective agents the term ID50 (infective dose 50) is used for the dose that has a 50% probability of producing a specified response to infection, considered in this report as symptoms or signs of disease or death.
Neither the LD50 nor the ED50 gives sufficient information in itself to form a guide to the relation between dose and effect.
The additional information needed is provided by the "slope of the probit line", which can always be calculated from the data required for the accurate determination of an ED50 (Finney, 1952, 1968).
This figure is dimensionless, so that its meaning is independent of the units of dosage.

At p. 88

Influence of local meteorological factors on the effectiveness of an attack with chemical weapons
…It appears that the probit lines of very toxic agents have high slopes.
It is legitimate therefore to take the critical distance as that at which the Ct corresponds to an LD50. This Ct is referred to as the LCt50. The probability of death will amount almost to certainty for an agent of high probit slope (5-10) when the Ct is only a little larger than the LCt50...

Vaccination — parenteral (outside the digestive tract) injection of mixtures of foreign biological material and synthetic chemicals — can be understood as maximizing exposure intensity or Ct: inserting the maximum concentration of poison into the living subject in the minimum amount of time.

Biologicals are “substances which cannot be fully characterized by physico-chemical means alone, and which therefore require the use of some form of bioassay.”
Biological tests (bioassay). A biological test is a laboratory procedure for the estimation of the nature or potency of a material by means of the reaction that follows its application to some elements of a living system (examples include animals, tissues, cells, receptors and enzymes). The potency of the material being measured is often defined in International Units or, in some circumstances, may be defined in terms of International System of Units (SI), by comparison with the reaction of the system to a biological reference preparation.
International biological measurement standards (commonly referred to as WHO International Standards, IS) are substances, classed as “biological” according to the criteria outlined above, which are provided to enable the results of biological assays or immunological assays to be expressed in the same way throughout the world. The value assignment by the World Health Organization is in terms of an International Unit (IU) or another suitable unit. The unitage is attributed to a first international standard in an arbitrary manner after an international collaborative study has been completed.

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