From: "Higgins 

To: Melanie King/RTP/USEPA/US@EPA 

cc: RobertJ Wayland/RTP/USEPA/US@EPA, Peter Tsirigotis/RTP/USEPA/US@EPA 

Date: Wednesday, February 17, 2010 01:00PM 

Subject: RICE -- edits 

History: This message has been replied to and forwarded.

Hi Melanie, 

I've attached a pdf of suggested changes to the RIA -- the first is to 

try to address concerns about ground level transport and the 

characertization, the second clarifies some of the hazardous constituent 

language. Please let me know if you have concerns about either of these 

or if you can work them into the RIA. 

Additionally, could you also consider the following: USDA still 

questions the assumption about the distribution of irrigation engines 

among major and area sources. Given the signature deadline, can you add 

some language to the source estimates memo, and possibly to the RIA, 

that states "For estimating the number engines located at major and area 

sources, we used our best engineering judgment, and we recognize that it 

may lead to an overestimate or underestimate of costs and benefits for 

certain sectors." Another suggestion is the following: " Given that few 

farms are known to be current major sources, less than 40% of the farms 

with RICE engines may be located at major sources, but EPA did not have 

available data to quantify an alternative estimate." 

Finally, is the limited use category for area sources supposed to be for 

engines greater than 500 or 300? The regulatory language and preamble 

uses a 500 threshold, but retrofits are required for area source engines 

greater than 300, and, the costs of retrofits for 300 HP engines running 

less than 100 hours a year does not exceed the low end of the benefits 

range. 

Please give me a call if you have questions. 

Regards, 

Cortney 

Attachments:

CI RICE NESHAP RIA 2-17-10_p133.pdf CI RICE NESHAP RIA 2-17-10_p119.pdf

Page 1 of 1

https://rtairmail1.rtp.epa.gov/mail/mking.nsf/($Inbox)/8465B14AC8C09A79718E0532B3... 2/17/2010
7-4 

The underlying emissions modeling and air quality modeling account for the current 

distribution of emissions sources, including both urban and rural sources. In addition, the air 

quality modeling included 14 vertical layers to simulate the differences between ground-level 

emissions and higher stack emissions (U.S. EPA, 2006a). The distance that particles travel 

primarily depends on the size of the particle and meteorological conditions, such as wind speed 

and precipitation. Fine particles can have an atmospheric half-life of days to weeks and travel 

hundreds to thousands of kilometers, whereas ultrafine and coarse particles travel less than ten 

kilometers (U.S. EPA, 2009c). Because we have not undertaken a study specific to emissions at 

ground level from RICE, with regard to transport issues and to size fraction of PM2.5 emissions 

(e.g., ultrafines and near ultrafines), there is uncertainty as to how far such emissions will travel 

and thus with regard to populations affected. Evidence from recent air quality modeling for 

mobile source rules with similar engines (U.S. EPA, 1999; U.S. EPA, 2000; U.S. EPA, 2004; 

U.S. EPA, 2008e; U.S. EPA, 2010c) shows that some fine particles can travel long distances in 

the atmosphere, but the proportion of such emissions from RICE that travel more than short 

distances under typical ground level meteorological conditions is not yet definitively known, 

thus introducing a potentially important source of uncertainty. 

The benefit-per-ton coefficients in this analysis were derived using modified versions of 

the health impact functions used in the PM NAAQS Regulatory Impact Analysis (U.S. EPA, 

2006b). Specifically, this analysis uses the benefit-per-ton method first applied in the Portland 

Cement NESHAP RIA (U.S. EPA, 2009a), which incorporated three updates: a new population 

dataset, an expanded geographic scope of the benefit-per-ton calculation, and the functions 

directly from the epidemiology studies without an adjustment for an assumed threshold.3

Removing the threshold assumption is a key difference between the method used in this analysis 

of PM co-benefits and the methods used in RIAs prior to that for the Portland Cement NESHAP, 

and we now calculate incremental co-benefits down to the lowest modeled PM2.5 air quality 

levels. 

EPA strives to use the best available science to support our benefits analyses, and we 

recognize that interpretation of the science regarding air pollution and health is dynamic and 

evolving. Based on our review of the body of scientific literature, EPA applied the no-threshold 

model in this analysis. EPA’s Integrated Science Assessment for Particulate Matter (U.S. EPA, 

2009c), which was recently reviewed by EPA’s Clean Air Scientific Advisory Committee (U.S. 

EPA-SAB, 2009a; U.S. EPA-SAB, 2009b), concluded that the scientific literature consistently 

 

3

 The benefit-per-ton estimates have also been updated since the Cement RIA to incorporate a revised VSL, as 

discussed on the next page. 
7-18 

strong respiratory irritants such as acrolein. 

Other Air Toxics

In addition to the compounds described above, other compounds in gaseous hydrocarbon 

and PM emissions from RICE engines would be affected by this rule. Information regarding the 

health effects of these compounds can be found in EPA’s IRIS database.59

The distance that these HAPs travel away from the emission source depends on several 

factors. HAPs such as formaldehyde, acetaldehyde, PAHs, and acrolein are emitted as gases. 

Regional photochemical model simulations, examining particular scenarios, have shown that 

gaseous HAPs like formaldehyde and acetaldehyde can be transported hundreds of kilometers 

from their emissions source in distinct plumes (U.S. EPA, 2010b). Further, these emissions can 

contribute to regional airmasses with elevated concentrations of gaseous HAPs. These polluted 

airmasses, under the scenarios examined, can be transported thousands of kilometers and affect 

locations well distant from the original emissions source. Some gaseous HAPs with higher 

molecular weight, such as toluene, can transform into particles in the atmosphere. For engines 

examined in this rule, EPA does not have enough information to determine how far each of the 

HAPs will travel. For In general, for HAPs emitted as particles, such as metals, the travel 

distance primarily depends on the size of the particle and meteorological conditions, such as 

wind speed and precipitation. Fine particles can have an atmospheric half-life of days to weeks 

and travel hundreds to thousands of kilometers, whereas ultrafine and coarse particles travel less 

than ten kilometers (U.S. EPA, 2009c). The level at which the emissions occur can also play a 

role in determining transport distances. For instance, ground level emissions are less likely to 

travel long distances when compared to particles emitted substantially above ground level.

Carbon monoxide co-benefits 

Carbon monoxide (CO) exposure is associated with a variety of health effects. Without 

knowing the location of the emission reductions and the resulting ambient concentrations using 

fine-scale air quality modeling, we were unable to estimate the exposure to CO for nearby 

populations. Due to data limitations, we were unable to estimate the benefits associated with the 

14,000 tons reductions in CO emissions that would occur as a result of this rule. 

Carbon monoxide in ambient air is formed primarily by the incomplete combustion of 

carbon-containing fuels and photochemical reactions in the atmosphere. The amount of CO 

 

59 U.S. EPA Integrated Risk Information System (IRIS) database is available at: www.epa.gov/iris