White Papers for Occupational Safety and Health Administration (OSHA)

OSHA Infectious Dose White paper

A pathogen’s infectious dose (ID) is one of many
factors that are considered when a biological hazard
analysis is performed. The NIH Recombinant DNA
Guidelines and the CDC/NIH Guidelines for Biosafety
in Microbiological and Biomedical Laboratories
recognize many factors interact and contribute
to an organism’s ability to infect the host. Since the
ID varies based on a number of factors, it is often
prudent to conduct specific job hazard analysis or
risk assessments to determine the appropriate precautions
used in a microbiological laboratory. Factors
to be considered in determining the level of containment
include agent factors such as virulence,
pathogenicity, infectious dose, environmental stability,
route of spread, communicability, operations,
quantity, availability of vaccine or treatment, and
gene product effects such as toxicity, physiological
activity, and allergenicity. The infectious dose of the
agent is another factor to consider. Infectious dose
can vary from one to hundreds of thousands of
units. The complex nature of the interaction of microorganisms
and the host presents a significant
challenge even to the healthiest immunized laboratory
worker, and may pose a serious risk to those
with lesser resistance. The laboratory worker’s immune
status is directly related to his/her susceptibility
to disease when working with an infectious agent
(NIH Guidelines, 2002; CDC-NIH, 1999). By analogy
with the LD50 metric that is used to communicate
chemical toxicity, OSHA has asked ABSA to
evaluate whether infectious dose would provide a
meaningful parameter for communicating the relative
and absolute risks of infectious agents.
In this paper, ABSA examines the current opportunities
associated with the development or extrapolation
of infectious dose values, and the subsequent
application of infectious dose in a regulatory
setting. ABSA has identified the challenges in defining
endpoints for the term “infection” (and consequently,
for “infectious dose”), and the challenges
associated with the interpretation of data from disparate
studies.
ABSA believes that the current internationally
recognized system for assigning pathogens to one of
four Risk Groups based on numerous factors is prudent
and has worked well over time, and should continue
to do so in the future. ABSA has concluded
that the vast amount of resources needed to develop
scientifically valid, quantitative values for infectious
dose, the potential assignment of permissible exposure
limits, and the subsequent sampling and laboratory
analyses that would then be required would not
improve worker protection. ABSA believes that
OSHA would see a better return in terms of worker
health and safety if these valuable and limited, human
and financial resources were used for promoting
other safety initiatives.

View the White Paper

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