PRINCIPLES OF TOXICOLOGY

32 GENERAL PRINCIPLES OF TOXICOLOGY
2. For the 95th percentile ingestion rate:
5.8 mg / kg per day
60 kg
1000
Fish concentration =
63 g / day
Fish concentration (95th) = 0.0055 mg/g = 5.5 µg/g or 5.5 ppm.
For the intake of fruits and vegetables, if we assume a daily mean consumption rate of 5.28 g/kg and
a 95th percentile daily consumption rate of 22.44 g/kg, once again, using the PCP as an example, a
safe vegetable and fruit concentration mean consumption rate could be calculated as follows:
Safe fruit–vegetable concentration = 0.001 mg/g = 1 µg/g = 1 ppm
To calculate the safe exposure levels for those individuals consuming fruits and vegetables at the 95th
percentile consumption rate we simply divide by 22.44 g/kg per day rather than 5.28 g/kg per day and
the safe fruit–vegetable concentration becomes 0.00025 mg/g = 0.25 µg/g = 0.25 ppm.
1.9 SUMMARY
Toxicology is a broad scientific field that utilizes basic knowledge of many other scientific disciplines.
• A toxicologist must understand these disciplines in order to discover and examine the variety
of adverse effects produced by any toxicant.
• A toxicologist must utilize an understanding of each particular toxicant’s adverse effects,
and the dose–response curves for these toxicities, to develop either antidotal therapies or
guidelines for risk prediction and prevention.
• A toxicologist uses dose–response relationships as a basic means of identifying the potency
and toxicities that determine a chemical’s relative hazards. Ultimately the dose–response
curve for the toxicity of greatest concern is used to develop exposure guidelines for the
human populations exposed to the chemical. These exposure levels may be dependent on
the route of exposure and the perceived sensitivity of the population exposed.
Many types of toxicity tests and different factors can affect the outcome of a test or create uncertainty
about its extrapolation to a heterogeneous human population.
• Often the inherent toxicity of a compound cannot be altered; in such cases the only way to
lower the risk is to lower the exposure.
• Likewise, when unknown compounds are suspected of posing a hazard, or when our
confidence in the estimate of their toxicity is poor, the only way to limit the risk and its
liability is to limit exposure.
REFERENCES AND SUGGESTED READING
Ballantyne, B., T. C. Marrs, and P. Turner. “Fundamentals of toxicology,” in General and Applied Toxicology, B.
Ballantyne, T. Marrs, and P. Turner, eds., M. Stockton Press, New York, 1993, pp. 3–38.
Ballantine, B., “ Exposure-dose-response relationships,” in Hazardous Materials Toxicology: Clinical Principles
of Environmental Health, J. B. Sullivan and G. R. Krieger, eds., Williams & Wilkins, Baltimore, 1992, pp.
24–30.