Principles of Environmental and Occupational Hazard Assessment

Details

• Personal Author:
  Crutchfield CD ; Sullivan JB Jr ; Van Ert MD
• Description:
  A fundamental precept of human toxicology is that the intensity of toxic action is a function of the concentration of the toxic agent that reaches a target organ or tissue. The relationship between concentration and intensity of effect is commonly referred to as the dose-response relationship for a given substance. Dose is defined as the amount or mass of contaminant that is absorbed or deposited in the body over an increment of time. The total dose experienced by an individual refers to the sum of doses resulting from all environmental contact with a contaminant received by a person over a given time interval. Biological measures of a chemical or its metabolites in various matrices, such as blood or urine, are seeing increased application as more direct indicators of dose (i.e., biological exposure indices). But in many instances, it is not practical to assess exposure by using exhaled air, blood, urine, or other biological specimens. It is often necessary to rely on exposure measurement as a surrogate for estimating dose. In the workplace and related environments, exposure measurement serves as a bridge between conditions of work and potential toxic effect. The concept of exposure is formally defined as an event that occurs when there is contact between a human and the environment with a contaminant of specific concentration for an interval of time. The unit of expression for exposure is: concentration x time. Exposure (or dose) profiles describe the exposure concentration ( or dose) as a function of time. Expressed differently, concentration and time are used to depict exposure while amount and time characterize dose. It is necessary to measure or estimate the exposure (dose) to appreciate the potential health effects from a substance. To use exposure as a surrogate for dose, certain assumptions are required to relate the duration of an exposure to expected effect. The implied assumption, called Haber's rule, states that the effect is proportional to cumulative dose. Dose is estimated by exposure concentration times the duration of the exposure. This straightforward relationship is used to express exposure as a function of contaminant concentration and time. What is lost in this expression is an appreciation for any variation in concentration that occurred during the averaging time. In an occupational setting, this relationship has resulted in the use of 8- or 40-hour averaging times to express acceptable levels of employee exposure. In certain instances, this concept has been expanded to express cumulative exposure over extended periods, such as parts-per-million (ppm)years. For example, Haber's rule implies that exposure to 100 ppm for 5 years is dose-equivalent to an exposure of 500 ppm for 1 year. Time-weighted averages (TWAs) are widely used in exposure assessments, especially as part of risk assessments for carcinogens. [Description provided by NIOSH]
• Subjects:
  Hazardous Substances Occupational Exposure Occupational Health Safety Toxicology
• Keywords:
  Biological Effects Chronic Exposure Dose Response Exposure Assessment Health Hazards Risk Assessment
• ISBN:
  9780683080278
• Publisher:
  Lippincott Williams & Wilkins
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Book
• Place as Subject:
  Arizona ; OSHA Region 9
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  30-49
• NIOSHTIC Number:
  nn:20055088
• Citation:
  Clinical environmental health and toxic exposures, second edition. Sullivan JB Jr, Krieger GR eds. Philadelphia, PA: Lippincott Williams & Wilkins, 2001 Jun; :30-49
• Editor(s):
  Sullivan JB Jr; Krieger GR
• Federal Fiscal Year:
  2001
• Performing Organization:
  University of Arizona, Tucson
• Peer Reviewed:
  True
• Start Date:
  19950701
• Source Full Name:
  Clinical environmental health and toxic exposures, second edition
• End Date:
  20060630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:982860403c94ff8ff23a3c13855a8b2f4f5b22fa92742d36c1cadbb36334cd7aeb5fd113bf435a6d4b8f1922dce9a2446b07352ee3c6a30645187c4ee47df385
• Download URL:
  https://stacks.cdc.gov/view/cdc/217459/cdc_217459_DS1.pdf
• File Type:
  [PDF - 2.67 MB ]