Toxicology Update Tiffany Bredfeldt, Ph.D. Toxicology Division Texas Commission on Environmental Quality Advanced Air Permitting Seminar 2015.

Toxicology Update

Tiffany Bredfeldt, Ph.D. Toxicology Division

Texas Commission on Environmental QualityAdvanced Air Permitting Seminar 2015

Updates

• New Odor White Paper• Updated Odor Values• Reminder to Use New ESL Forms• Database in Progress

Why Do We Regulate Odors?

• Odor - leading cause of citizen complaints• Required by the Texas Clean Air Act• What is the role of the odor-based ESL?–Prevent odor nuisance conditions–Not necessarily odor detection

New Odor White Paper

• Approach to odor ESL derivation has changed

• New approach uses a weight of evidence evaluation

• Visit the Toxicology website for more information

Odor White Paper: Why Change?

• Odor data is highly variable• The reason for the variance is unclear• The purpose of an odor-based ESL is

to prevent nuisance• The goal is to produce a list of odor

ESLs consistent in the manner in which they are derived

Odor: Previous Approaches

• Collect odor thresholds:–Odor detection threshold - concentration at which a

certain percent of a panel of humans detects odor–Odor recognition threshold - concentration at which

a chemical is recognized specifically– The 50% odor detection threshold is typically used

Odor: Previous Approaches• For chemicals with reported thresholds, the

50% odor detection threshold was used• If more than one OD50 was available, a

geometric average was taken• If data was considered of lower quality, the

lowest OD50 was taken

• For chemicals without odor detection thresholds, generic odor values were derived based on structure-activity relationships or chemical class

Previous Approaches: Pitfalls

• Odor threshold data are highly variable• Newer methodologies may be very

sensitive and may result in bias • If older values have not resulted in an

odor complaint, should we change the value to newer data?

Odor: Updated Approaches• Process is similar• Steps:– Identify odor character– Is the chemical potentially malodorous?– Search for available odor threshold data

• Agency records may guide the decisions regarding the odor ESL used

• Not all chemicals will have odor ESLs • The focus is upon chemicals that

could cause nuisance

Not all chemicals smell bad

Isoamyl acetate

Cis-rose oxideBeta-damascenoneBeta-ionone

Limonene

Methyl salicylate

OcimenolCinnamyl alcoholEthyl-2-methoxybenzoate

Some chemicals smell bad

TrimethylamineAmmoniaHydrogen SulfideMethane

2-Butene-1-thiol3-Methyl-1-butanethiol

1,5-Pentanediamine1,4-Butanediamine

Odor: Updated Approaches

• If there is evidence that a chemical may cause odor nuisance but only at high concentrations, higher thresholds may be used

• Examples:–Acetaldehyde–Propionaldehyde

• Odor recognition threshold may be used

Example: Propionaldehyde

• Previous value (OD50): 22 µg/m3

• Odor is described as fruity at lower concentrations

• Upon evaluation of available monitoring data, this value has been detected at sites where the odor was described as sweet by field investigators

• New value (OR50): 95 µg/m3

Odor: Updated Approaches

• When selecting odor-based values:–Consider odor character–Determine odor if odor character is

ubiquitous or dependent on concentration– Identify available odor thresholds–Research past values used (if any) and

whether any odor complaints are associated with this chemical– Select odor threshold

Odor: Other Changes• No generic odor values will be used anymore

(e.g., amines or carboxylic acids odor value)• Instead, when odor values are not available,

ESLs will be surrogated to chemicals with similar structure

• Values for chemicals where odor is described as mild or pleasant will not be derived

• In those cases, health values will be used• All odor ESLs were reviewed at the same time• Consistent application of new guidance

Odor Summary • Some approaches to how we derive odor-

based ESLs have changed• We will still derive odor ESLs as needed for

chemicals anticipated to be malodorous• Detection or recognition thresholds may be

used as the basis• New odor values may be seen in the updated

database• And on our website

Additional Updates

• ESL Documentation• ESL Database Project

TCEQESLs

Internet

ESL Documentation• New form to fill out for ESL requests• The paperwork processed during ESL

derivation has changed within the Toxicology Division

• That means that ESL derivations may take a bit longer due to the way records are generated and placed into a format that will be used for the database

• Expect a longer turnover time

ESL Documentation• Make sure that you fill out the ESL request form• When consultants or companies ask for an ESL

for a specific chemical:– Check current ESL list– Fill out ESL request form– Get additional information (i.e., MSDS, physical

chemical properties, etc.)

Chemical Information

ESL Documentation

• Documentation may have slowed turn around time

• We are releasing a new ESL list this fall• Please remember to check our website

for ESLs• New list will be publicized via the

Toxicology Announcements (e-mail)

Database• The ESL database is still in the process of being

generated• Some issues with getting it coded• When complete, it should run through the public

database TAMIS• In PROGRESS!• Keep up with the

Toxicology Division Announcements online

Thank you for your attention

Tiffany [email protected]

512-239-1799