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API 4419

1985 Edition, 1985

Complete Document

Review of Published Odor and Taste Threshold Values of Soluble Gasoline Components



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Product Details:

  • Revision: 1985 Edition, 1985
  • Published Date: December 1985
  • Status: Not Active, See comments below
  • Document Language: English
  • Published By: American Petroleum Institute (API)
  • Page Count: 53
  • ANSI Approved: No
  • DoD Adopted: No

Description / Abstract:



EXECUTIVE SUMMARY

This report has been prepared by TRC Environmental Consultants, Inc. for the Environmental Biology and Community Health Committee of the American Petroleum Institute. It represents the results of Tasks 1and 2 of a three task study: Task 1, a literature search for the published odor and taste threshold values of the 276 soluble components of gasoline; Task 2, a critique of the methodologies used to develop the thresholds reported; and Task 3 , a recommended experimental protocol for the determination of odor and taste threshold values for soluble gasoline components (under preparation). In addition, the taste and odor thresholds of five alcohols (methanol, ethanol, isopropanol, t-butanol, n-propanol) and one ether (MTBE) were obtained.

Threshold Definitions

There are two basic types of thresholds - detection and recognition. The detection threshold is defined as the lowest concentration of stimulus that can be discriminated from stimulus-free blanks. The recognition threshold is the lowest concentration of stimulus that can be described as possessing a character (i.e., sweet, rancid). Neither threshold describes avoidance - the concentration level of stimuli that would be avoided (i.e., desist smelling or tasting). The avoidance threshold information is also useful in that it may be important to know the level that gasoline components in drinking water will be detected and acted upon in addition to when they can be detected.

Odor

Published odor thresholds were found for only 51 of the 282compounds including the five alcohols and one ether. A set of thirteen criteria were developed by TRC as minimum requirements fora valid odor threshold determination procedure. If all thirteen were applied to the published data. no threshold values would be accepted. Therefore, three of these criteria were used to accept or reject the published odor thresholds for inclusion in this study. The three key criteria are:

1. Odorants were presented to panelists in an ascending concentration series.

2 . The maximum concentration interval between stimuli presentations did not exceed a factor of three.

3. The panel used for threshold determination contained more than five individual judges.

Of the 51 compounds with published odor thresholds, only 21 had thresholds which met these three criteria. From the 21 threshold values, the geometric mean of the published thresholds meeting these criteria, was calculated to develop the odor threshold. Threshold's that did not meet the criteria showed a maximum difference in concentration (mg/m3) between lowest and highest published values of 312,500. For those determinations that complied with the three criteria, the resulting range of values showed a maximum 300-fold difference between lowest and highest concentration. For example, benzene has 24 published values only four of which passed the criteria. The range for the 24 values was from 0.05 to 495 mg/m3; the range for the four acceptable values was from 38 to 380 mg/m3.

Taste

Published taste thresholds were found for only five of the compounds. A set of twelve criteria were developed as requirements for valid taste threshold determinations. Two of these criteria were used to accept or reject the published taste thresholds:

1. A panel of greater than five individual judges.

2. A two-fold concentration step between successive stimuli presentations.

Only two compounds had published taste thresholds that met these two criteria. These taste thresholds are summarized as follows: ethanol79 mg/l (detection); MTBE .7 mg/l (detection), 5 mg/l (recognition).