What’s your hygiene MPD?

May 1, 2005
Are you counting your yearly dosage of MPDs? Do you know what your yearly hygiene radiation dosage of MPDs are?

Are you counting your yearly dosage of MPDs? Do you know what your yearly hygiene radiation dosage of MPDs are?

We take patient X-rays each day and work inches away from Panorex machines, yet we assume our radiation exposures added together are safe! I recently became aware of a personal health issue that might be related to overexposure to scattered dental radiation. I have worked in the dental field full time for 20 years, and I never gave a moment’s thought to radiation dosage accumulation in my body. I became complacent about wearing a radiation badge until I was educated about the absorption of scatter radiation inside my own thyroid gland.

As practitioners, we might be absorbing too much scatter radiation. Most dental offices I have worked in take the standard X-ray precautions. But with the increase in out-of-office background environmental radiation concerns, do we need to rethink X-ray accumulation and yearly limits in dosage absorption within our dental office environment?

The four major types of ionizing radiation are Alpha, Beta, Gamma, and X-rays. The weakest are Alpha and Beta. Their penetration rate is less than a sheet of paper or a few millimeters of aluminum. They are not a serious threat unless they are ingested.

Gamma and X-rays are quite powerful and potentially very dangerous. These X-rays are produced from man-made sources such as X-ray tubes, arcs, and lamps. They can pass through virtually anything except materials of high atomic weight such as lead. Because of their penetrating ability, X-rays are used to see inside the human body, destroy cancer cells, and analyze the internal structure of rocks and minerals.

The sun and other space bodies transmit “cosmic radiation” and produce gamma rays naturally. These cosmic radiations, along with radioactive earth minerals, combine to produce “background count,” a measurement used in addition to calculating total radiation dosage per year per person. This particular radiation is always present on earth. The background effect should always be factored in or subtracted from overall dosage limit readings.

What household items can emit radiation? We return home after working on patients all day. Since we have left the office, we are safe from radiation, right? I thought so until my research revealed perhaps not.

Some common items at home emit radiation in low dosages, such as smoke detectors, which emit alpha and beta rays. Old camera lenses contain thorium. Certain gems in jewelry are irradiated by the radioactive element radium, X-rays, or other particles to produce a color change, which makes the gems radioactive. Rocks and minerals such as uraninite and carnotite, to name a couple, are also radioactive. Older antique pottery glazed with uranium oxide, as well as furniture made with certain metal objects, are reported to be partly made of spent radioactive material. These are some home items to consider regarding radiation.

How much radiation exposure is too much?

The United States Air Force Dental Investigation Service addressed this question at their Annual Dental Radiation Safety Briefing in October 2004. Are there limits? Yes! The limit is called Maximum Permissible Dose (MPD). This is the amount of radiation received chronically or acutely over a lifetime which (in light of present knowledge) is not expected to cause appreciable body injury.

The occupational dose is 10 times higher. Occupational personnel are assumed to accept a higher risk of radiation for the lifestyle attained by employment. MPD limits for the occupationally exposed amounts to 20 mSv/yr (new 1998 standard). In comparison, the limit for the general public is 1 mSv/yr, and pregnant women 5mSv/9 months.

Radiation protection points to consider for practitioners include position (out of primary beam), distance (minimum six feet away), and shielding (barriers, aprons, walls).

All of us know to leave the room when taking X-rays, and to stand at least six feet away from the X-ray machine, but these may not be a complete solution. We also need to calculate “background radiation” into our mSv/ per year. Background radiation is called Gamma Rays. Not only do we have to calculate our in-office exposure, but also our out-of-office exposure.

We would be well served to know how much dosage over the course of a year we are absorbing, just to be on the safe side. Never assume that just because we currently do not show signs of illness that we might not become ill later due to accumulation and biological side effects in our bodies.

While doing research I discovered an old/new technology called a Geiger counter. While it’s well known in engineering circles and hospital settings, I had never heard of this in the dental office setting. This instrument can measure real-time scatter radiation. It has the capacity to give instant information. The X-ray badges we clip onto our clothing need months of collecting data, while the Geiger counter measures our scatter radiation dosage that instant.

Geiger counters have been around for years and recently became pocket-sized and digital with software applications. The one I prefer is the Inspector Digital Pocket Geiger Counter, which is a hand-held pocket model. Simply leave it on all day connected to your operatory computer. The Inspector includes a software application which gives a digital graph read out of your scatter radiation exposure over the course of the day, month, and year. It has excellent sensitivity detection to low levels of Alpha, Beta, Gamma, and X-rays. This is important because it will give information we need to collect for dosage limit amount in real time.

We may never exceed our dosage for the year, but for those of us who have any kind of biological tissue sensitivity in our bodies or are pregnant, we now have the tool to accurately measure instant indications of radiation levels. For more information about a Geiger counter, go to www.geigercounters.com.

I have only touched on the beginnings of X-ray protocol. We live in an ever-changing environmental world. I realize I may have to rethink the way I have been practicing dental hygiene, particularly X-rays, in order to protect myself and my co-workers. The one change happening in our dental office is the introduction of digital X-rays. The X-ray sensors are a significantly lower dosage than film.

Digital X-ray sensors are significantly lower than film, but it would still be safer to measure scatter radiation, even if your office implements digital X-rays. The X-ray unit may emit a lower radiation dosage, but is our body absorbing the lower dosage radiation and not knowing it? That question remains to be answered with more research.

Your doctor may not take the responsibility to investigate scatter radiation inside his or her office since he or she delegates this task. Perhaps emulating the medical profession and keeping up-to-date with a Geiger counter is an easy and inexpensive solution to change and safety. The only side effect is better biological health and safety for the dental team.

What could be better than that?

Victoria DaCosta, RDH, BS, is founder and president of Hy-Tech Solutions. A practicing dental hygienist for 18 years, DaCosta is a speaker, author, consultant, and an expert in the design of medical/dental software. She is also on the new technologies committee for the California Dental Hygienists’ Association. DaCosta can be contacted at www.hy-techsolutions.com.