### MEMORANDUM

TO: Nhan Nguyen

FROM: Maj’d El-Zoobi

DATE: December 2, 2008

SUBJECT: Review of Inhalation Monitoring Study for the of P-07-601

The submitter of P-07-601 submitted the subject matter study as an alternative assessment to CEB’s assessment of inhalation exposure at th e of P-07-601.

The review of this study was tasked to ER G’s industrial hygienist who was provided with guidelines for conducting the review that are based on your directive on this matter which you sent to me on 8/12/08.

This memorandum contains the subject matte r, which includes the following items:

- a brief presentation of the results of the study;

- a summary of ERG’s review comments on the study;

- a summary of my comments on the study;

As further discussed below, I assess the submitter’s study to contain some significant transparency flaws, and to possibly be deficient in regard to the number of samples taken. These concerns may be addressed through discussion with the submitter, and likely additional monitoring.

The recommended alternative path forward is to maintain CEB’s assessed average and maximum values of ppm and ppm respectively in lie u of additional monitoring. It is noted that the average value of ppm is comparable to th e highest average exposure level reported in the submitter’s inhalation monitoring study, which is ppm, which supports the use of ppm as a valid assessed value. The assessed maximum va lue of ppm is maintained even though it significantly exceeds the level of ppm because there is uncertainty in the results of the submitter’s inhalation monitoring study. This maximum value is an TWA value.Presentation of the Results of the Study and Comparison With the Current Assessment :

Inhalation Exposure Concentration Assessed Values

CEB’s Current Assessment Submi tter Inhalation Monitoring Study Worker Activity 8 hr TWA Exposure concentration (ppm) Comments 8 hr TWA Exposure concentration (ppm) Comments

Other Available Inhalation Exposure Concentration Data Worker Activity CEB Data Submitter Data

Personal samples Note (1): Table A-6, “Summary of Personal Occupational Exposure Monitoring Data for Manufacture of ”, Occupational Exposure And Environmental Release Data for and Their Substitutes, PEI Associates, 1990.

The vapor pressure and boiling point of (the GS basis), mmHg and C, are comparable to the corresponding va lues for the NCS, which are mmHg and C, respectively. Hence the GS data is valid for comparison purposes.

Note (2): These two data points, the e xposure levels for , which is ppm, and the exposure level for the , which is ppm, may be di scarded because they appear to be for specific job functions in the manufacture of that do not have an equivalent in the manufacture of the new chemical.

Summary Of ERG’s Review Comments On The Study: The following is excerpted from ERG’s report on their review of the study. The complete ERG report is attached at the bottom.

Summary of Limitations:

• Additional monitoring should be conducted to account fo r the exposure variability associated with the work environment a nd random sampling and analytical errors. Specifically, a total of at leas t six full-shift personal brea thing zone (PBZ) samples should be collected over six different days to adequa tely characterize worker exposure to the two refrigerants.• Information regarding the daily duration of exposure should be provided according to individual job titles, includi ng a total number of workers by each job title that could potentially be exposed to these two chemicals.

• Exposure criteria for workers at bo th facilities have been based on an work shift but the possibility of workers workin g shifts which could exceed the shift duration has not been considered.

• The study does not indicate the total number of workers by each job title that could potentially be exposed to the two refrigerants.

Additional information to incorporate into the monitoring study/report for completeness includes:

o The manner in which the number of samples collected was determined.

o The manner in which the number of work ers to be monitored was determined.

o The reason specific job classifications or specific individuals were selected for monitoring. Typically, workers with the gr eatest potential for exposure must be included.

• The study does not provide information on wh ether there may be other tasks with the potential for worker exposure; e.g., tasks pe rformed by workers that might be involved in non-routine activities.

• Exposure criteria for workers at both facilities have b een based on an work shift but the possibility of workers working shifts whic h could exceed the sta ndard shift duration has not been considered.

• No information was available from the report on vari ables such as:

o The age of the plant.

o The age of the control equipment.

o Operation and maintenance (O&M ) practices at the plant.

o Production levels.

• The monitoring report includes no discussion regarding the occupational exposure limits (OELs) for and . Further, the study fails to discuss the monitoring results by comparing them to the OELs for the two .

• Personal protective equipment (PPE) worn by the workers sampled, if any, was not identified in the report.

Summary Of My Comments On The Study The report does provide a descriptio n of plant operations worker activities, but it does not clearly indicate whether there are other ta sks that may result in exposure le vels that are higher than what was sampled.

Also, the report does not consid er exposure of workers.