HAP benefits

Due to data, resource, and methodology limita tions, we were unable to estimate the benefits associated with the 1,014 tons of hazard ous air pollutants that would be reduced as a
result of this rule. Available emissions data show that several different HAPs are emitted from stationary engines, either c ontained within the fuel burned or formed during the combustion process. The HAPs measured in emission test s conducted on diesel fired stationary RICE include 1,3-butadiene, acetaldehyde, acrolein, be nzene, ethylbenzene, formaldehyde, n-hexane, naphthalene, polycyclic aromatic hydrocarbons (PAHs), polycyclic organic matter, styrene, toluene, and xylene. Metallic HAPs from diesel fired stationary RICE that have been measured include cadmium, chromium, lead, manga nese, mercury, nickel, and selenium.

Although numerous HAPs may be emitted from RICE, a few HAPs account for 80% of
the total mass of HAPs emissions from diesel stationary RICE. These HAPs are formaldehyde (25%), acetaldehyde (19%), PAH (18%), naphthalene (9%), and acrolein (9%).

• Formaldehyde is the HAP emitted in the larg est quantities from stationary RICE. Acute and chronic exposures to formalde hyde may irritate the eyes, nose, and throat, and may cause coughing, chest pa ins, and bronchitis. Reproductive effects, such as menstrual disorders a nd pregnancy problems, have been reported in female workers exposed to formaldehyde. Limited human studies have reported associations between formal dehyde exposure and lung cancer, nasopharyngeal cancer, and possibly leukemi a. Animal inhalation studies have reported an increased incidence of nasal squamous cell cancer. EPA classifies formaldehyde a probable human carcinogen. 1

• Acute exposure to acetaldehyde may result in irritation of the eyes, skin, and respiratory tract. In humans, symptoms of chronic exposure to acetaldehyde resemble those of alcoholism. Long-ter m inhalation exposure studies in animals have reported damage to the nasal ep ithelium and mucous membranes, growth retardation, and increased kidney weight. EPA has classified acetaldehyde as a probable human carcinogen based on nasal tumo rs in rats and laryngeal tumors in
hamsters. 2

1 Summarized from EPA’s Hea lth Effects Notebook. Ava ilable on the Internet at http://www.epa.gov/ttn/atw /hlthef/formalde.html
2 Summarized from EPA’s Hea lth Effects Notebook. Ava ilable on the Internet at http://www.epa.gov/ttn/atw /hlthef/acetalde.html• Polycyclic aromatic hydrocarbons (PAHs) are a broad class of compounds whose molecules are composed of fused aromatic carbon rings, and whose toxicity varies widely depending on molecular structure. Dermal exposures to environmental
mixtures of PAHs cause skin disorders in humans and animals. An increase in lung cancer has been reported in human s exposed to PAH-bearing mixtures including coke oven emissions, roofing tar emissions, and cigarette smoke. Animal studies have reported respiratory tract tumors from inhalation exposure to one PAH compound, benzo[a]pyrene. Th e EPA has classified seven PAH compounds as probable human carcinogens. 3

• Acute exposure to naphthalene can cause hemolytic anemia (with symptoms of fatigue, lack of appetite, restlessness, a nd pale skin) as well as nausea, vomiting, diarrhea, blood in the urine, and a yellow color to the skin. Chronic exposure to naphthalene has been reported to cause cat aracts and damage to the retina. EPA has classified naphthalene as a Group C, possible human carcinogen. 4

• Acute inhalation exposure to acrolein may result in upper respiratory tract irritation and congestion. The major eff ects from chronic (long term) inhalation exposure to acrolein in humans consist of general respiratory congestion and eye, nose, and throat irr itation. Acrolein is a strong derm al irritant, causing skin burns in humans. Data are not adequate fo r an assessment of the human carcinogenic potential of acrolein. 5

The distance that these HAPs travel away from the emission source depends on several factors. HAPs such as formaldehyde, acetaldeh yde, PAHs, and acrolein are emitted as gases. Regional photochemical model simulations 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 can be transported
thousands of kilometers and affect locations well distant from the original emissions source. Some gaseous HAPs transform into particles in the atmosphere. For HAPs emitted as particles, such as metals, the travel distance primar ily depends on the size of the particle and meteorological conditions, such as wind speed and precipitation. Fine pa rticles can have an

3 Summarized from EPA’s Hea lth Effects Notebook. Ava ilable on the Internet at http://www.epa.gov/ttn/atw /hlthef/polycycl.html
4 Summarized from EPA’s Hea lth Effects Notebook. Ava ilable on the Internet at http://www.epa.gov/ttn/atw/hlthef/naphthal.html
5 Summarized from EPA’s Hea lth Effects Notebook. Ava ilable on the Internet at http://www.epa.gov/ttn/atw/hlthef/acrolein.htmlatmospheric half-life of days to weeks and trav el hundreds to thousands of kilometers, whereas ultrafine and coarse particles travel less than ten kilometers (U.S. EPA, 2009c).