>> In this module, we will discuss why we need
radiation epidemiology.
We know that radiation can cause cancer.
So, why do we need radiation epidemiology at all today?
We know about radiation health effects
when the exposures occur all at once or briefly,
such as among the atomic bomb survivors.
But, what we really don't know clearly is what happens
when exposure is spread over time, and received gradually.
For example, all of us, not only radiation workers,
are exposed to low doses
of radiation every day of our lives.
We don't get a one-shot exposure all at once; we get it gradually
over time and over our lifespan.
What is the risk or the probability that this type
of exposure will result in cancer?
Is the risk from comparable radiation doses lower, the same,
or higher than seen
in the Japanese atomic bomb survivor data,
which are today the primary basis for radiation standards
and protection guidance?
Consider these sources of exposure to the public
and workers- medical radiation exposures in diagnostic imaging
and treatment, issues dealing with reactor accidents
such as Fukushima and the exposures to nearby residents,
terrorist events that could occur and we plan for.
Some occupations today experience exposures
that are not inconsequential,
such as fluoroscopy guided interventionalists,
and industrial radiographers.
Environmental exposures such as Technologically Enhanced
Naturally Occurring Radioactive Material or TENORM,
which is naturally occurring radioactive materials
that have been concentrated or exposed as a result
of human activities such as manufacturing,
mineral extraction, or water processing.
Radon in our homes.
Nuclear waste, both high level and low level.
Issues for astronauts traveling beyond Earth's orbit are
of concern.
And the even more relevant exposures are to pilots,
air crew and passengers who are flying higher
and more frequently than ever before.
We live in a veritable sea of low-level radiation
from the environment, in medicine
and in certain occupations,
and radiation epidemiology remains a needed cornerstone
to understand levels of potential risk
and to provide guidance for decision makers and managers
who must deal with current and future sources
of radiation exposure.
Why is there a concern in medical practice?
The numbers of CT and medical imaging examanations given
in the United States are increasing at a very high rate.
They were about 60 million per year just over 10 years ago
and now have reached over 80 million per year.
Medical exposures have become the number one source
of exposure to the U.S. population,
surpassing ubiquitous natural background radiation,
which includes radon, cosmic rays, environmental
and ingested radioactive substances,
such as the radioactive potassium
in bananas and other foods.
Because of the number of medical imaging exams
and the associated dose levels from multiple exams,
it's essential to better understand what the magnitude
of potential health effects might be,
to accurately estimate them and act to minimize the dose
to patients and reduce unnecessary imaging.
This theoretical future risk is to be balanced
with the immediate medical benefit.
So assessing risks and finding ways for preventive action
in medicine are of critical concern; for this,
radiation epidemiology is required.
What about radiological accidents
and intentional events?
After the Fukushima reactor accident there was wide-scale
contamination around that plant and in areas
where the winds deposited the radioactive releases.
Concerns at the time even included the dispersal
of radioactive releases around the world;
small but inconsequential radioactive debris was detected
in the United States and other countries.
A careful assessment of health risks
and projected risks was the realm of radiation epidemiology.
What about radiation poisoning and intentional events?
The ex-Russian spy who defected to London, Alexander Litvinenko,
was poisoned with a drop of polonium-210 in a cup
of tea before going to a sushi bar for dinner.
He died a horrible and painful death in 25 days.
He looked emaciated and as if he was treated with a lethal dose
of whole-body radiation.
Biokinetic models developed in conjunction
with epidemiologic studies of polonium workers were used
to accurately estimate the amount ingested
and doses to specific organs.
This is evidence of an intentional use
of radiation for harm.
Another concern is the widespread contamination
that would follow a radiological incident,
which would expose populations to elevated levels of radiation
for decades or longer.
Radiation epidemiology would help estimate the level
of risk possible if residents returned to their homes
and to help inform judgments of return or relocation.
It's also important to plan
for radiation emergencies before they occur.
In January 2018, the state of Hawaii issued a false alert
that a nuclear missile, a horrific weapon
of mass destruction, was heading their way.
Fortunately, the threat
of a nuclear weapon detonation was not real,
but the public concern was real.
Though the probability for such an attack is very small,
it is not zero.
An improvised nuclear device, or a radiological dispersal device,
also known as a "dirty bomb,"
could be intentionally detonated on US soil.
We plan in the United States
for such catastrophic events including the aftermath.
We need good estimates of potential radiation risks faced
by the emergency responders, the exposed populations,
and the populations returning to contaminated soil afterwards.
How about occupational exposures to radiation?
There are some occupations in medicine,
the interventional fluoroscopists,
where relatively high occupational exposures are
of concern.
How about industrial radiographers?
These are the workers who go out in the field
and use radioactive sources to test welds
and pipelines for integrity.
They can receive relatively high amounts of radiation;
in terms of occupational limits,
some even get close to the limit.
Each year, there are reports of worker accidents that result
in serious skin lesions,
formerly called deterministic effects
and now are called tissue reactions.
Interestingly, this is not a male dominated occupation
in that one-third of the industrial radiographers
in our epidemiologic studies are female.
It may also be surprising to learn
that the largest occupationally exposed group
in the United States today, in terms of collective dose,
are pilots and aircrew.
This is because of the large numbers and the doses received,
although individual doses do not exceed limits set
for terrestrial workers.
The reasons are because they fly higher and more frequently
than before and have increased cosmic ray exposures,
primarily from neutrons.
Assessments of their exposures in flight are to continue.
Radiation epidemiology can project risks,
and provide evaluations needed for informed decisions
as to whether interventions should be considered.
What about radiation levels around a nuclear power plant,
and cancer clusters reported
from living near nuclear facilities?
Are there reasons to be concerned?
Epidemiology provides insights.
What about radon?
It remains an important population exposure we
experience in our homes.
Recently, the highest levels of radon ever detected
in U.S. homes were recorded in Pennsylvania -
over 40% of homes were above the Environmental Protection
Agency's action guidance.
Epidemiology continues to provide improved estimates
of risk from home exposures.
Our homes shouldn't be health hazards!
What about cleaning up the radioactive waste
from legacy sites, such as former weapons facilities
or uranium and radium processing plants.
How clean is clean?
How low is low?
What is the target level for remediation,
for environmental cleanup?
The lowest level provides, theoretically, the lowest level
of risk; but the cost can be significant,
and the actual protection afforded might be miniscule.
What guidance can epidemiology provide
for the decision makers and managers?
Technologically enhanced naturally occurring radioactive
materials or TENORM is also an issue
because of the radioactive elements
that accompany oil and gas extraction.
What about exposures to radiation in space?
The limiting factor for our astronauts going
to Mars is radiation.
They'll receive the equivalent
of one whole-body CT exam every two days.
It's going to take them about three years for their mission-
to go there, explore, and return.
That's a lot of whole-body CT exams!
And you can imagine that the amount
of radiation they'll receive
from galactic cosmic rays is substantial
and could approach an effective dose of 1 Sv.
In comparison, each year we receive about 2.4 mSv
from natural background radiation.
There is also concern that women are more susceptible
to radiation-induced lung cancer than men.
This possibility increases the lifetime risk
of radiation-induced cancer, and limits the time
that women are allowed in space.
Radiation epidemiology is attempting to provide answers
to the risk from gradual exposures
from galactic cosmic rays in humans, the possible effect
on brain function, and whether there are differences
in lung cancer risk following radiation among men and women.
To summarize, there are many radiation exposure situations
that the public and professionals encounter,
and there are important public and individual health decisions
to be made regarding managing of these exposures.
Radiation epidemiology can provide valuable information
in this regard.
We need to have the best science
to make good radiation protection decisions,
set standards and provide guidance for occupational
and environmental exposures, as well as continue
to provide accurate and meaningful calculations
for ongoing dose reconstruction or dose estimation
and compensation programs.
And let's not leave out the need for radiation professionals,
radiation epidemiologists, radiation biologists,
radiation chemists, professors of radiation at universities,
radiation regulators, and more.
Having robust radiation health programs
in universities can ensure there is a pipeline
for radiation professionals to meet our future needs.