by Bernard L. Cohen

University of Pittsburgh


(published in the August 1999 HPS Newsletter)


A former ICRP Chairman supports the linear-no threshold theory

(LNT) because it simplifies bookkeeping. LNT is certainly convenient for

making health physics calculations. It allows us to calculate the risk

from any given radiation exposure in quantitative terms, which is the goal

of any risk analysis. Without LNT, the risk to a person from a given dose

depends on the concentration of radon in his home, his experiences with

medical X-rays, etc; effectively, there is a synergism between a given

exposure and all other radiation exposures. Since most of the latter are

unregulated, it is impractical to take them into account. If we abandon

LNT, we largely abandon quantitative risk assessment, which might seem to

make regulation more difficult.

But is this really a very serious problem? It is a problem that

occurs in nearly every other area of environmental concern. For example,

LNT is not used for air pollution. There are regulations on releases and

on ambient levels of SO2, of NOx, of total suspended particulates, of fine

particulates, of ozone, of lead, etc. For none of these can the risk of

each additional exposure be calculated quantitatively., even if no other

pollutants are present. No consideration is given to synergisms between

these various pollutants, although such synergisms are quite likely to be

important. By the standards we apply to radiation, the scientific bases

for air pollution regulations are mediocre at best.

But they work quite successfully. They prevent catastrophes and

generally avoid identifiable deaths. Most importantly, they give the

public confidence that it is being protected. This confidence is not even

shaken by studies concluding that tens of thousands of Americans die

annually from air pollution1. The Media give scant attention to these

studies, and the public shows little interest as long as no victims are

identifiably tied to the pollution..

Is this situation reprehensible? I think not. It allows our

technology to progress and to increase Society's wealth, and technology

and wealth create health, far outstripping the harm to health done by the

pollution. Air pollution reduces our life expectancy by something like 30

days2, whereas technology and the wealth it has created have increased our

life expectancy by 30 years in this century.

We thought we could do much better with radiation, using LNT to

calculate risks in quantitative terms. For every little bit of radiation,

we calculate the number of deaths, and killing is something the Media are

quick to report. People are moved by such reports and view these deaths as

real, perhaps even afflicting themselves or their loved ones. The public

has thus been driven insane over fear of radiation, losing all contact

with reality. As a result, we have largely lost the benefits of nuclear

power which could be averting tens of thousands of deaths per year from

air pollution (and also solving other environmental problems like global

warming, acid rain, etc). We are losing many other benefits of radiation

such as food irradiation which could be averting millions of cases of food

poisoning, saving thousands of lives, each year. We are wasting our

Society's wealth on ridiculous clean-up programs at nuclear facilities;

this wasted wealth could save thousands of lives each year if it were

spent on biomedical research, on public health programs, or on highway


Our passion for doing much better for radiation than has been done

for air pollution by using LNT has backfired horribly, costing our Society

dearly. Perhaps it could be argued that we must be honest and scientific

at all costs. But is accepting LNT honest science? I have reviewed this

question in detail in a recent paper3 and concluded that it is not. The

Health Physics Society Position Paper of January 1996 concludes that the

science does not exist for supporting LNT in the low dose region. The

situation is the same as for low levels of air pollution -- the science

just isn't there. The best they can do is regulate by assuming a threshold

for harm, and that is the best we can do for regulating radiation. Far

from making regulation of radiation more complicated as is often assumed,

this would greatly simplify our regulatory process

Thus, there is no honest scientific reason why radiation should be

treated differently than air pollution in the low dose region We should

abandon this phony effort to be more scientific in our regulatory

practices. That way we would be more honest, and we would have a much more

positive impact on the Society we serve.



1. H. Ozkaynak and J.C. Spengler, Analysis of health effects resulting

from population exposure to acid precipitation, Environmental Health

Perspectives 63:45ff; 1985


2. B.L. Cohen, Catalog of risks extended and updated, Health Physics

61:317-335; 1991


3. B.L. Cohen, Validity of the linear-no threshold theory of radiation

carcinogenesis in the low dose region, Technology 6:43-61; 1999