BOARD MEETING DATE: April 3, 2009
AGENDA NO. 18

PROPOSAL:

Notification of State-Approved Reference Exposure Levels for Acetaldehyde, Acrolein, Arsenic, Formaldehyde, Manganese, and Mercury

SYNOPSIS:

Rules 1401 – New Source Review of Toxic Air Contaminants and 1402 – Control of Toxic Air Contaminants from Existing Sources, require that staff notify the Board and affected parties before risk values for toxic air contaminants are added to or changed in Rule 1401.  On December 19, 2008, the Office of Environmental Health Hazard Assessment approved new and changed reference exposure levels (RELs) for several compounds:  acetaldehyde, acrolein, arsenic, formaldehyde, manganese, and mercury.  At a later Board meeting staff will propose addition of these RELs to Rule 1401. 

RECOMMENDED ACTION:

Receive and file.
 

Barry R. Wallerstein, D.Env.
Executive Officer

Background

On December 19, 2008, the Office of Environmental Health Hazard Assessment (OEHHA) adopted new acute, 8-hour, and chronic reference exposure levels (RELs) for acetaldehyde, acrolein, arsenic, formaldehyde, manganese, and mercury. RELs are associated with non-cancer health impacts, either from long-term (chronic) or short-term (acute) exposures to the compound and represent exposures or doses at or below which adverse health effects are not likely to occur. The Office of Environmental Health Hazard Assessment (OEHHA) establishes risk values for toxic air contaminants (TACs) and the Scientific Review Panel reviews and finalizes these values. Once OEHHA has adopted a risk value, Rules 1401 – New Source Review of Toxic Air Contaminants and 1402 – Control of Toxic Air Contaminants from Existing Sources require staff to notify the Board and affected parties of OEHHA’s actions and that risk values for toxic air contaminants are proposed to be added to or changed in Rule 1401. This Board letter serves as the notification.

The RELs recently adopted by OEHHA were evaluated by the Scientific Review Panel using a new methodology which was developed for OEHHA’s draft “Air Toxics Hot Spots Program Technical Support Document for the Derivation of Noncancer Reference Exposure Levels” (TSD). The Scientific Review Panel approved the final versions of the methodology section of the TSD on June 18, 2008. The new methodology reflects scientific knowledge and techniques developed since the previous Air Toxics
“Hot Spots” guidelines were prepared, and includes consideration of possible differential effects on the health of infants, children, and other sensitive subpopulations. The new methodology takes into consideration the physiological, biochemical, and behavioral differences between adults and infants and children. In addition to the new methodology, data from recent health studies were used to derive the RELs. As a result, some of the amended values are more stringent and some are less stringent than previously identified.

At a later Board meeting, staff will propose amendments to Rule 1401 to add the new and changed RELs and identify potential impacts on permitted sources and/or other environmental impacts. The proposed amendments to Rule 1401 will establish the implementation schedule for use of the new REL values for new equipment subject to Rule 1401 and existing facilities subject to Rule 1402.
 

New and Changed RELs Adopted December 19, 2008

Acetaldehyde

A new acute REL was adopted by OEHHA and the current chronic REL was made less stringent for acetaldehyde. A higher chronic REL indicates a higher dose level at or below which no adverse health impacts are expected. The new values are shown in Table 1. The major acute effects of human exposure to acetaldehyde vapors consist of irritation to the eyes, skin, and respiratory tract and bronchoconstriction in asthmatics. Chronic exposure affects the respiratory system.

Acetaldehyde is a colorless liquid or gas and is commonly used as an intermediate for the manufacture of a number of other chemicals. Permitted sources which may have acetaldehyde emissions include manufacturers of chemicals, wood-based building products such as fiberboard, particleboard, sheet vinyl flooring, and carpeting.
 

Acrolein

Both the acute and chronic REL values for acrolein were changed by OEHHA and both are less stringent than previous values. Acute effects of acrolein exposure affect the eyes and chronic exposure affects the respiratory system. The new values are show in Table 1.

No impacts are expected for permitted sources of acrolein due to the amended REL values because the values are less stringent than the previously values. Acrolein is a colorless or yellow liquid with a piercing disagreeable odor. Its principal industrial use is as a chemical intermediate in the production of acrylic acid and its esters. It is also a product of combustion.
 

Arsenic and Inorganic Arsenic Compounds including Arsine

Both the acute and chronic REL values were changed for inorganic arsenic. The new acute value is less stringent than the previous value. The chronic value is more stringent than previously. Acute arsenic exposure has developmental, cardiovascular, and nervous system effects. Chronic exposure has developmental, cardiovascular, nervous system, lung, and skin effects. Arsenic also has an oral pathway. The new values are shown in Table 1.

Industries with permitted sources of arsenic emissions that may be impacted by the more stringent chronic REL for arsenic compound include metal processes; pesticide manufacturing; ceramics; pharmaceuticals; and semiconductor manufacturing. Ore refining processes, including the smelting of copper and lead, are the major sources of the release of arsenic compounds. Processes such as smelting, galvanizing, soldering, and etching, that require the treatment of metal with strong acids are possible sources of arsine gas. Arsine gas may also be a by-product of the combustion of digester gas and landfill gas.
 

Formaldehyde

Both the acute and chronic REL values were changed for formaldehyde. The new acute value is more stringent than the previous value and the chronic value is less stringent. Acute formaldehyde exposure may result in mild to moderate eye irritation. Chronic exposure may cause nasal obstruction and discomfort, lower airway discomfort, and eye irritation. The new values are shown in Table 1.

Several permitted industries with formaldehyde emissions may be affected by the addition of the more stringent acute REL for formaldehyde to Rule 1401. The four major applications of formaldehyde are as an intermediate in the manufacture of melamine, polyacetal, and phenolic resins; as an intermediate in the production of industrial chemicals; as a bactericide or fungicide; and as a component in the manufacture of end-use consumer products. Permitted sources which produce plywood, particleboard, foam insulation, and molded or extruded plastic items may also be impacted. Formaldehyde is also a product of fuel combustion, including natural gas, so large permitted facilities such as power generators and oil refineries may be impacted.
 

Manganese and Manganese Compounds

The chronic REL for manganese was changed and the new value is more stringent than the previous value. Chronic exposure to manganese affects the nervous system. The new chronic REL value is shown in Table 1.

Metallic manganese is used in many permitted manufacturing processes. Manganese is used in the manufacturing of steel, carbon steel, stainless steel, cast iron, and superalloys to increase hardness, stiffness, and strength. Other permitted processes with manganese emissions include textile printing and dyeing; battery manufacturing; pharmaceutical and food manufacturing; ceramics and colored glass industries; paint manufacturing; and fertilizer and fungicide manufacturing. Manganese is also used as an octane enhancer in some unleaded gasolines and is released during fuel combustion.
 

Mercury and Inorganic Mercury Compounds

Both the chronic and acute RELs for mercury were changed and the new values are more stringent than the previous values. Chronic exposure to mercury may affect the nervous system. Acute exposure may affect development and the nervous system. Mercury also has an oral pathway. The new values are shown in Table 1.

Mercury and mercury-containing compounds are widely used. Permitted facilities which use mercury in the manufacture of thermometers, barometers, and thermostats may be affected by the new RELs. Mercury is commonly used for these applications due to its uniform volume expansion over a broad temperature range. Permits for industries which use mercury to make mercury arc and fluorescent lamps; as a catalyst in oxidation of organic compounds; as a cathode in electrolysis may be affected. Other industries that may be impacted include pulp and paper manufacturing; battery manufacturing; dental amalgam manufacturing; manufacturing of switching devices such as oscillators; and manufacturing of chlorine and caustic soda. To a lesser extent permits may be affected at facilities that use mercury as a grain fumigant, in agricultural chemicals, in pharmaceuticals, as a preservative, as a lubricant, and as a laboratory reagent.
 

Relative Exposure Levels

Table 1 lists the new or changed RELs for the specified compounds. It also lists a screening level which represents a conservative estimate of the amount of the compound which could be emitted in a year for chronic impacts or in one hour for acute impacts below which no adverse impacts would reasonably be expected for a receptor at a distance of 25 meters from the source of the emissions.
 

Table I – Chronic and Acute Reference Exposure Levels and Screening Values

*The cancer screening values for acetaldehyde and formaldehyde are more stringent than the chronic screening values. Therefore, the screening value based on cancer risk will be used as the screening value in AQMD’s “Risk Assessment Procedures for Rules 1401 and 212”.