Dr. Brett Rosenberg, PhD, CHP, Senior Health Physicist at NV5
Insurance is something people don’t like paying for—until they need it. Part of insurance involves risk evaluation and protection. Dosimetry serves as a form of insurance for companies, providing assurance for workers who may have been exposed to radiation.
Exploring Dosimetry: Types and Practices for Monitoring Occupational Exposures
Dosimetrists can proactively assess the risk of exposure, or the dose linked to a specific job. They are adept at determining the extent of radiation a worker may have encountered—whether in proximity (external dosimetry) or absorbed into the body (internal dosimetry) following an exposure. Each form of dosimetry presents unique technical challenges, underscoring the importance of having experts in these specialized roles. Operational challenges may also arise, potentially impeding the monitoring of individuals and the reporting of exposures to regulatory agencies, as stipulated by the Code of Federal Regulations.
External dosimetry is often considered the more cost-effective and automated dosimetry option. The assessment of a person’s external exposure to radiation relies on the use of a badge worn by the worker. This badge contains materials sensitive to various forms of radiation. An algorithm is employed to analyze the doses the worker may have received to the skin, lens of the eye, and the entire body, based on interactions within the sensitive material. The frequency of dosimeter administration depends on the expected dose for the worker, with higher doses typically necessitating more frequent ‘exchanges’—periods between collecting the old dosimeter and assigning a new one.
Internal dosimetry has several nuances that require an understanding of the work being performed, the form of the radioactive material being handled, and how that material is processed within the body. Different analyses can be conducted on a single bioassay sample (e.g., alpha spectrometry and mass spectrometry for a urine sample), or different bioassay samples can undergo the same analysis (e.g., alpha spectroscopy of urine, alpha spectroscopy of feces). There is a technical basis for the type of analysis, the material analyzed, and the frequency of sampling. Due to the sample processing involved for urine and fecal samples, internal dosimetry can be seen as more expensive, invasive, and inconvenient. And, unlike dosimeters, sample kits cannot be reused and must be considered in the cost of an internal dosimetry program.
Both dosimetry forms are essential for regulatory compliance under the Code of Federal Regulations, constituting a crucial component of a company’s health and safety program. Failure to return dosimeters promptly, submit bioassay samples on time, or adhere to work restrictions constitutes interference with effective monitoring for worker health and safety. Background radiation can disrupt occupational dose measurements for dosimeters, while delayed bioassay sampling may lead to undetected intakes due to increased excretion.
Instances of dosimeter and sample delinquency may be more prevalent in dispersed work locations, environments with a low health and safety culture, or where communication and worker training are insufficient. To address these challenges, effective practices include establishing convenient exchange locations for dosimeters and samples, enforcing work restrictions, providing additional training, and increasing management involvement in health and safety aspects.
Routine or confirmatory programs can be employed to make sure workers are adequately monitored for intakes of radioactive material while maintaining convenience and affordability. A routine monitoring program could mandate all workers involved in radiological work to provide bioassay samples on a prescribed basis. This is especially beneficial for a large workforce supporting a diverse set of projects with unique hazards that may lead to radiological exposures surpassing administrative control levels or regulatory limits.
On the other hand, a confirmatory program involves only a fraction of the workers, ideally selecting those most likely to have had exposures, to provide samples for confirmation if an intake occurred. However, managing the aftermath of a detected intake can be challenging, contingent on the program’s infrastructure. It is crucial to establish traceability for identifying the individuals who performed the work and determining when the potential exposure took place.
For external dosimetry, providing a dosimeter to anyone concerned about potential external exposure, including support staff not directly involved in radiological work, may seem straightforward. However, a dosimeter result indicating a minor exposure for a non-radiological worker could cause undue concern. It’s essential to recognize that natural background radiation rates fluctuate, and doses from the environment and medical exposures can surpass occupational doses by several times. Nevertheless, not everyone wearing a dosimeter possesses this level of understanding.
To address this, deploying area dosimeters in spaces with high occupancy levels can offer assurance. Area dosimeters serve as a form of insurance, demonstrating that exposures within the general workforce are known and within regulatory limits. This approach may also serve as a cost-saving measure and alleviate challenges associated with the collection and distribution of individual dosimeters.
When choosing the optimal approach, various factors come into play. NV5’s dosimetry experts are ready to assist you and your business in evaluating applicability and addressing any inquiries. For guidance, contact us at 509.946.0410 or reach out to Dr. Brett Rosenberg, Senior Health Physicist, via email at brett.rosenberg@nv5.com . The distinctive technical challenges associated with each form of dosimetry emphasize the significance of having experts in these specialized roles.