Toxicology l.jpg
This presentation is the property of its rightful owner.
Sponsored Links
1 / 20

Toxicology PowerPoint PPT Presentation


  • 115 Views
  • Uploaded on
  • Presentation posted in: General

Toxicology. Presented to ES-317y at UWO in 1999 Dick Hawrelak. Consequences to Humans. Consequences of toxic chemical exposure are usually derived from animal experiments (rats, mice, dogs, etc.). Search the internet for “Holocaust” for the exception to this statement.

Download Presentation

Toxicology

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Toxicology l.jpg

Toxicology

  • Presented to ES-317y at UWO in 1999

  • Dick Hawrelak


Consequences to humans l.jpg

Consequences to Humans

  • Consequences of toxic chemical exposure are usually derived from animal experiments (rats, mice, dogs, etc.).

  • Search the internet for “Holocaust” for the exception to this statement.


Uncertainties in animal data l.jpg

Uncertainties in Animal Data

  • The uncertainties in translating small animal data to data relevant for humans are large and therefore safety factors are included in the modeling.


Acute versus chronic injury l.jpg

Acute Versus Chronic Injury

  • Emergency planners generally deal with acute or short term lethal injury (2000 people died in a few days in Bhopal toxic release).

  • Environmentalists deal with longer term chronic injury (eg cancer after 20 years of exposure).


Two acute categories l.jpg

Two Acute Categories

  • Local Irritantia (LI) deals with direct damage to the lungs.

  • Sytematically Acting Agents (SAA) deals with damage to the body via the blood and distribution in the body.


Local irritantia l.jpg

Local Irritantia

  • LC50(h,30) = [3.3/10][LC50(r,30) (for rats).

  • Animals have a higher adsorption rate, safety factor set at 5

  • Humans have a higher respiratory rate in accident situations, safety factor set at 2

  • Hence, a safety factor of 10 is used in LI.


Systematically acting agents l.jpg

Systematically Acting Agents

  • LC50(h,30) = [5.1/20][LC50(r,30)

  • A large uncertainty factor of 10 is introduced for blood effects.

  • Humans have a higher respiratory rate in accident situations, safety factor set at 2.

  • Hence a safety factor of 20 is used in SAA.


Convert animal data to humans l.jpg

Convert Animal Data to Humans

  • Once experimental data is available, a standard regression line is drawn through all the converted data (Animals to Humans).

  • The data is plotted as LN(time) as the x-axis and LN(Conc) as the y-axis.


H2s data l.jpg

H2S Data


Standard deviations about the regression line l.jpg

Standard Deviations About the Regression Line.

  • One standard deviation covers 67% of the data points.

  • Two standard deviations covers 95% of the data points.

  • The regression line is assigned LC50.

  • The mean + 2SD is assigned LC99.

  • The mean - 2SD is assigned LC01.


Probits l.jpg

Probits

  • The data between LC99 and LC01 can be converted to regular standard intervals by the use of a probit equation.

  • Pr = a + b Ln[(C^n)(t)]

  • n = 1 / m where m is the slope of the regression curve. Ln is the Natural Log.

  • a and b are constants to suit the intermediate LC values.


Probit chart for h2s l.jpg

Probit Chart For H2S


Two databases for toxic chemicals l.jpg

Two Databases for Toxic Chemicals

  • The UK database as in CPQRA of the CCPS / AIChE.

  • The Dutch database as in Prince Maritus lab (Green Book by TNO).

  • The two databases give different answers for acute injury rates.

  • The differences remain unresolved and are being debated in academia.


The holocaust data for hcn l.jpg

The Holocaust Data for HCN

  • CPQRA gives a fatal dose at 5 minutes for 2,000 ppmv exposure.

  • TNO gives a fatal dose at 0.5 minutes for 2,000 ppmv exposure.


Other conflicting data l.jpg

Other Conflicting Data

  • Industrial hygienists have used STEL, TLV, ERPG1, ERPG2 and IDLH for years.

  • These concentration / time values should mesh smoothly with the acute time / concentration data.

  • Often adjustment have to be made to have a set of data that is satisfactory to both industrial hygienists and emergency planners.


Probit program l.jpg

Probit Program

  • Toxic consequences can be determined using the Probit Data V1.1 program in Chemical Plant Hazards \ Toxics \ Toxicology \ Probit Data V1.1 files.

  • The user selects a chemical from the dB, a probit method, a concentration and an exposure time.

  • The program determines the consequence as shown on the following example.


Probit data v1 1 l.jpg

Probit Data V1.1


Probit data v1 1 chart l.jpg

Probit Data V1.1 Chart


H2s animal data l.jpg

H2S Animal Data

  • As an example of the above procedure, the Concord Scientific Data for H2S is presented in Chemical Plant Hazard \ Toxics \ Toxicology \ H2S Data file.

  • This technology is quite complex and is generally offered at the graduate level.

  • Work is in progress to make this more understandable at the undergraduate level.


Possible exam question l.jpg

Possible Exam Question

  • Describe acute versus chronic injury.

  • What two databases are available that describe the toxicity of certain chemicals?

  • ***


  • Login