Throughout the past decade much research has been directed towards identifying the occurrence, epidemiology, and risks
associated with waterborne protozoa. While outbreaks are continually documented, sporadic cases of disease associated
with exposure to low levels of waterborne protozoa are of increasing concern. Current methodologies may not be sensitive
enough to define these low levels of disease. However, risk assessment methods may be utilised to address these low level
contamination events. The purpose of this article is to provide an introduction to microbial risk assessment for waterborne
protozoa. Risk assessment is a useful tool for evaluating relative risks and can be used for development of policies to
decrease risks. Numerous studies have been published on risk assessment methods for pathogenic protozoa including
Cryptosporidium and Giardia. One common notion prevails: microbial risk assessment presents interesting complications
to the traditional chemical risk assessment paradigm. Single microbial exposures (non-threshold) are capable of causing
symptomatic illness unlike traditional chemical exposures, which require a threshold to be reached. Due to the lack of
efficient recovery and detection methods for protozoa, we may be underestimating the occurrence, concentration and
distribution of these pathogenic micro-organisms. To better utilize the tool of microbial risk assessment for risk
management practices, future research should focus in the area of exposure assessment.
Current Status and Issues of Risk Assessment for Hydrogen Transport
