Relative%20Toxicity

1
Relative Toxicity
2
If the response-dose curve for chemical A is to
the right of r-d curve for chemical B, then B is
more toxic. However,
3
Threshold Dose

• The lowest value on the response vs. dose curve
  is called the threshold dose. Below this dose the
  body is able to detoxify and eliminate the agent
  without any detectable effects.

4
Threshold Limit Values (TLV)

• Established by the American Conference of
  Governmental Industrial Hygienists (ACGIH).
• The TLV refers to airborne concentrations that
  correspond to conditions where no adverse effects
  are normally expected during a workers lifetime.
• The exposure occurs only during normal working
  hours, eight hours per day and five days per week.

5
TLV-TWA

• Time weighted average for a normal 8-hour workday
  or 40-hour workweek, to which nearly all workers
  can be exposed, day after day, without adverse
  effects.
• Excursions above the limit are allowed if
  compensated by excursions below the limit.

6
TLV-STEL

• Short-term exposure limit. The maximum
  concentration to which workers can be exposed for
  a period of up to 15 minutes continuously without
  suffering (1) intolerable irritation, (2) chronic
  or irreversible tissue changes, (3) narcosis of
  sufficient degree to increases accident
  proneness, or materially reduce worker
  efficiency, provided that no more than four
  excursions per day are permitted, and provided
  that the daily TLV-TWA is not exceed.

7
TLV-C

• Ceiling limit. The concentration which should
  not be exceeded, even instantaneously.

8
Permissible Exposure Level (PEL)

• Defined by the United States Occupational Safety
  and Health Administration (OSHA).
• The PEL values follow the TLV-TWA very closely.
  However, they are not as numerous and are not
  updated as frequently. The TLVs are more
  conservative.

9
IDLH

• Amount immediately dangerous to lif and health.
• Established by National Institute of Occupational
  Safety and Health (NIOSH).
• See Appendix 5 for TLV, PEL and IDLH data.