Calculation of adjusted TLV-TWA for toxic chemicals for Titan II Missile Launch Crew Members 24 hour work schedule.

Bottom line: UDMH exposure based on 24 hour shift exposure using references and correct sampling calculation procedures from OSHA, NIOSH, and ACGIH.

Silo (By the missile) DSV Crew Members at 570-6 were exposed to (8) eight times the adjusted ACGIH limit allowed starting in 1995.

Non Silo DSV Crew Members at 570-6 were exposed to exposed to (6.4) times the ACGIH adjusted limit allowed starting in 1995.

Not including other breakdown chemicals or skin absorption.

DSV=Daily Shift Verification.

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PROOF OF CLAIMS:

The information below was derived from the 2003, 2005, 2012 ACGIH manual's. I will continue to add more information as it is updated from ACGIH in future.

"ACGIH in the 2003 TLVs® and BEIs® refers to the Brief and Scala model and the Pharmacokinetic Model (found in Patty’s Industrial Hygiene) as a "tentative" guideline for industrial hygienist dealing with extended work shifts.

There are four steps to determining how much over exposed to the toxic fuels each of us were based on the DM AFB study of normal UDMH, NDMA, and Hydrazine concentrations in the silo and launch control center.

First, we must modify the 1995 UDMH 10 ppb TLV-TWA ACGIH allowed limits based on work schedule. The 10 ppb is based on a normal 8 hour work shift per day five days a week. There were very few jobs around the Titan II missiles that had that typical civilian work schedule (Bankers hours). The 10 ppb TWA on Hydrazine and UDMH must be reduced according to ACGIH guidelines.

Second, we must calculate the actual 8 hour Time Weighted Average for the UDMH sample period from the flawed DM study.

Third, we must figure out our actual exposure based on our travels throughout the Titan II missile Complex based on the DM Titan II complex toxic study of 1983. See botched DM study.

Fourth, we must then account for all the other toxic breakdown chemical TLV-TWA's including the skin exposure which is worse than inhalation. We may never know the actual percentages of the other breakdown chemicals from the Aerozene 50. We may be able to estimate them at some point.

FROM ACGIH - Unusual Work Schedules http://www.acgih.org/Products/tlv_bei_intro.htm

Application of TLVs® to work schedules markedly different from the conventional 8-hour day, 40-hour workweek requires particular judgment to provide protection for these workers equal to that provided to workers on conventional work shifts. Short workweeks can allow workers to have more than one job, perhaps with similar exposures, and may result in overexposure, even if neither job by itself entails overexposure.

Numerous mathematical models to adjust for unusual work schedules have been described. In terms of toxicologic principles, their general objective is to identify a dose that ensures that the daily peak body burden or weekly peak body burden does not exceed that which occurs during a normal 8-hour/day, 5-day/week shift. A comprehensive review of the approaches to adjusting occupational exposure limits for unusual work schedules is provided in Patty’s Industrial Hygiene (Paustenbach, 2000). Other selected readings on this topic include Lapare et al. (2003), Brodeur et al. (2001), Caldwell et al. (2001), Eide (2000), Verma (2000), Rouch (1978), and Hickey and Reist (1977).

Another model that addresses unusual work schedules is the Brief and Scala model (1986), which is explained in detail in Patty’s Industrial Hygiene (Paustenbach, 2000). This model reduces the TLV® proportionately for both increased exposure time and reduced recovery (i.e., non-exposure) time, and is generally intended to apply to work schedules longer than 8 hours/day or 40 hours/week. The model should not be used to justify very high exposures as “allowable” where the exposure periods are short(e.g., exposure to 8 times the TLV–TWA for 1 hour and zero exposure during the remainder of the shift). In this respect, the general limitations on TLV–TWA excursions and TLV–STELs should be applied to avoid inappropriate use of the model with very short exposure periods or shifts.

The Brief and Scala model is easier to use than some of the more complex models based on pharmacokinetic actions. The application of such models usually requires knowledge of the biological half-life of each substance, and some models require additional data. Another model developed by the University of Montreal and the Institute de Recherche en Sante et en Securite du Travail (IRSST) uses the Haber method to calculate adjusted exposure limits (Brodeur et al., 2001). This method generates values close to those obtained from physiologically based pharmacokinetic (PBPK) models.Because adjusted TLVs® do not have the benefit of historical use and long-time observation, medical supervision during initial use of adjusted TLVs® is advised. Unnecessary exposure of workers should be avoided, even if a model shows such exposures to be “allowable.” Mathematical models should not be used to justify higher-than-necessary exposures.

I chose to use the Pharmacokinetic Model based on the 24 hour work schedule as the half life of UDMH is given in several references. Based on another reviewer of the methods available he stated the following:

Pharmacokinetic Model (Patty’s Industrial Hygiene Toxicology)

Calculates to give same peak body burden

Considers half life of product

Graphs make it easy

Technically the most “accurate” of the 3 models

This Pharmacokinetic Model calculates what the adjusted TLV-TWA exposure limit for UDMH should be based on the Crew member work schedule of 24 hours.

This method takes the half life of UDMH which has been calculated to be up to 7.7 Hours in a study conducted in 1991 (Howard). Using the following graph the factor multiplied by the current ACGIH TWA of 10 ppb is .65. so our new ACGIH TWA exposure limit (for 24 hours exposure) would be 6.5 ppb and not 10 ppb.

The flawed DM Bioengineering TWA calculation used the wrong equation for the 262 minute short sample period. See correction calculation. The correct measured TWA 8 hour UDMH in the LCC at site 570-6 should have been 42 ppb based on OHSA instructions. So, at 570-6 we were exposed to 6.4 times the toxic UDMH amount allowed today for a 24 hour work day.

Those of us (like me) who volunteered for 48 hour Alert test program at DM in 1977-1978 where exposed to more. From the graph below the new adjusted TLV-TWA would have been 5.5 ppb based on 2 day alert.

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Using Equation 3-1b and saying that the two crew members that did Daily Shift Verification (DSV) went in the silo for four hours and in the LCC for four hours we can estimate the added toxic exposure to UDMH based on the DM study.

In the silo at the equipment area level six the UDMH readings were 152µg/m3 for 236 min according to DM Bioengineering.

So, putting the LCC and the Silo equipment area actual readings into the equation we have: ((103µg/m3)(262 min)+(152µg/m3)(236 min)/262 min+236 min = 26986+35872/498=126µg/m3 converting to ppb (24.45)(126)/60.1 = 51.4 ppb TWA (8 hour only) actual calculated TWA This still does not account for 24 hour work schedule which means to adjust the ACGIH allowed UDMH limit to 6.4 ppb instead of 10 ppb!

So, 51.4 ppb UDMH/6.4 ppb = 8. DSV Crew Members were exposed to eight times the limit allowed starting in 1995.

In my case during my 48 hour alert test program, for one year, I was over exposed by 51.4 ppb/5.5ppb TWA adjusted = 9.3 times over exposed. And of course I was stationed at 571-4 the second worst site of the five sites tested at Davis Monthan Air Force Base in 1983.

From: http://www.wiley.com/WileyCDA/WileyTitle/productCd-0470074884.html

http://www.amazon.com/Pattys-Industrial-Hygiene-Toxicology-Biological/dp/0471530654

(Patty’s Industrial Hygiene is referred to in the OSHA regulations, NIOSH and ACGIH)