COMMENTS BY RICHARD C. HERTZBERG, PH.D., ATLANTA, GA 

Thank you. A recent letter to the editor in our Atlanta Journal Constitutic11 claimed 

that the EPA carbon rule and purported benefits are "based on flawed science". That 

is an easy claim to make, because nearly all science has some flaw, some facet 

where we wish we knew more. But the writer's conclusions about the application of 

the carbon rule and its benefits are absurdly wrong. Instead of countering those 

arguments, I want to add to EPA's statements of why we need action now. 

I am a private consultant in biomathematics and an adjunct professor in 

Environmental Health at Emory University where I teach environmental health risk 

assessment. One of my classroom goals is to involve real environmental scenarios 

with real populations. In so doing, we address "cumulative risk," the risk from the 

combination of all the contaminants and stressors that we encounter at the same 

time. Why is that important to the support of the carbon rule? In the latest U.S. 

National Climate Assessment report, it says: 

"Climate change is increasing the risks of heat stress, respiratory stress from poor air 

quality, and the spread of waterborne diseases." 

Elsewhere it states: 

"Heat waves are also associated with increased hospital admissions for 

cardiovascular, kidney, and respiratory disorders." 

EPA Administrator McCarthy, on EPA's website, says 1 in 10 children have asthma. 

In recent studies of some major cities, including the Oakland area and Detroit, they 

found about 1 in 3 children were on asthma medication. One in Three. 

EPA estimates how many asthma attacks and premature deaths woulclbe avoided 

by the required cuts in traditional air pollutants. Where EPA could go fur• her when 

discussing the health benefits is to consider not just the separate risks, but the 

cumulative impact of all stressors together. My research specialty is toxic 

interactions, synergy and antagonism among chemicals. Of most conc0m for public 

health is synergy, where the combination exposure is significantly more toxic than a 

sum of individual exposures or risks would predict. So yes, we have re~;ulations on 

ozone, and on particulate matter (PMs), and on many other contamina1·ts in air. And 

we worry about effects of air pollution and heat waves on children. But our concerns 

should be much greater because of the combination effect of these stressors. Is 

there such evidence? 

When evaluating health impacts of climate change, some studies estirn::_te the 

increase in ozone and its consequences on acute asthma attacks. Or h:w marry die 

from heat waves. Or the impacts of particulate matter on several disease rates. I am 

concerned that the EPA's estimates of health benefits from the carbon rule are 

similarly based on evaluations of each pollutant or condition by itself. That can and 
should be changed. Some very fine epidemiology studies over the past 4 0 years 

here and in Europe looked at the health consequences of air pollution in combination 

with heat waves. Famous epidemiology studies over 50 years ago, such as those on 

cigarette smoke, "controlled for" the other factors, so to identify the contribution fmm 

the one pollutant of interest, such as cigarette smoke. But that single po lutant risk 

estimate does not represent a Real Exposure. In welcome contrast, these recent 

studies looked at the composite exposure conditions: real exposures to ozone, PMs 

and heat waves all together. They found significantly increased risks from the 

combination for acute asthma and for early mortality. But the situation gets wmse. 

Another study on air pollution and asthma shows synergy with psychological stress 

from neighborhood violence. And where are many regions with high neifJhborhaod 

violence? Large cities. We thus have defined a highly vulnerable populaion and one 

of considerable size. 

The science of toxic interactions is complex, expensive, and difficult to quantify, one 

main reason why so few regulations incorporate interactions. While we know rnJch 

about mechanisms for high temperatures enhancing particulate matter toxicity and 

for PMs enhancing ozone toxicity, we have not modeled the 3-way interaction, nor 

the 4-way combination that includes stress. 

But these interaction effects have been documented and are already occurring to 

vulnerable populations, including children and the elderly. We see these exacerbated 

effects in asthma visits at emergency rooms, and in increased mortality. These are 

not minor annoyances, but serious health conditions. 

So should EPA delay inclusion of interactions because we do not have 2. 

mathematical dose-response model? NO! As stated in EPA's own guidance for 

chemical mixtures risk assessment, even when only subjective information exists on 

the combination effects, those joint effects must still be characterized tc the extent 

possible and reflected in the risk assessment. 

In summary, EPA is doing precisely what is needed with this Carbon Ru.e, by acting 

NOW. Do not wait until all the desired mechanistic understanding and dose-response 

modeling have been accomplished. The interaction evidence is strong. rhe health 

impacts are here today, so we need action today. 

Thank you for your attention.