Abstract  A number of the compounds proposed as replacements for substances controlled under the Montreal Protocol have extremely short atmospheric lifetimes, on the order of days to a few months. An important example is n-propyl bromide (also referred to as 1-bromopropane, CH2BrCH2CH3 or simplified as 1-C3H7Br or nPB). This compound, useful as a solvent, has an atmospheric lifetime of less than 20 days due to its reaction with hydroxyl. Because nPB contains bromine, any amount reaching the stratosphere has the potential to affect concentrations of stratospheric ozone. The definition of Ozone Depletion Potentials (ODP) needs to be modified for such short-lived compounds to account for the location and timing of emissions. It is not adequate to treat these chemicals as if they were uniformly emitted at all latitudes and longitudes as normally done for longer-lived gases. Thus, for short-lived compounds, policymakers will need a table of ODP values instead of the single value generally provided in past studies. This study uses the MOZART2 three-dimensional chemical-transport model in combination with studies with our less computationally expensive two-dimensional model to examine potential effects of nPB on stratospheric ozone. Multiple facets of this study examine key questions regarding the amount of bromine reaching the stratosphere following emission of nPB. Our most significant findings from this study for the purposes of short-lived replacement compound ozone effects are summarized as follows. The degradation of nPB produces a significant quantity of bromoacetone which increases the amount of bromine transported to the stratosphere due to nPB. However, much of that effect is not due to bromoacetone itself, but instead to inorganic bromine which is produced from tropospheric oxidation of nPB, bromoacetone, and other degradation products and is transported above the dry and wet deposition processes of the model. The MOZART2 nPB results indicate a minimal correction of the two-dimensional results in order to derive our final results: an nPB chemical lifetime of 19 days and an Ozone Depletion Potential range of 0.033 to 0.040 for assumed global emissions over landmasses, 19 days and 0.021 to 0.028, respectively, for assumed emissions in the industrialized regions of the Northern Hemisphere, and 9 days and 0.087 to 0.105, respectively, for assumed emission in tropical Southeast Asia.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. RRM NOTE RESEARCH ARTICLE WISTAR RAT MALE FEMALE 1-BROMOPROPANE TOXICOKINETICS TOXICITY HEPATIC METABOLISM PARTITION COEFFICIENT ANEMIA AMENORRHEA OLIGOSPERMIA HEPATIC MICROSOMES 2-BROMOPROPANE TOXICOLOGY BLOOD AND LYMPHATIC DISEASE REPRODUCTIVE SYSTEM DISEASE-FEMALE REPRODUCTIVE SYSTEM DISEASE-MALE KOREA PALEARCTIC REGION

Abstract  The existing solvents trichloroethylene (TCE) and perchloroethylene (PCE) and proposed solvent n-propyl bromide (nPB) have atmospheric lifetimes from days to a few months, but contain chlorine or bromine that could affect stratospheric ozone. Several previous studies estimated the Ozone Depletion Potentials (ODPs) for various assumptions of nPB emissions location, but these studies used simplified modeling treatments. The primary purpose of this study is to reevaluate the ODP for n-propyl bromide (nPB) using a current-generation chemistry-transport model of the troposphere and stratosphere. For the first time, ODPs for TCE and PCE are also evaluated in a three-dimensional, global atmospheric chemistry-transport model. Emissions representing industrial use of each compound are incorporated on land surfaces from 30 degree N to 60 degree N. The atmospheric chemical lifetime obtained for nPB is 24.7 days, similar to past literature, but the ODP is 0.0049, lower than in our past study of nPB. The derived atmospheric lifetime for TCE is 13.0 days and for PCE is 111 days. The corresponding ODPs are 0.00037 and 0.0050, respectively.

Abstract  We have updated the analysis of the atmospheric lifetimes and ozone depletion potentials (ODPs) of chlorobromomethane (CH2ClBr) and l-bromo-propane (CH2BrCH2CH3 or simplified as 1-C3H7Br) based on a new version of our two-dimensional chemical-transport model of the global atmosphere. in the previous analysis of these compounds, now published in Atmospheric Environment, Wuebbles et al. (1997) had determined an ODP of 0.11-0.13 for CH2ClBr and an ODP of 0.006 for 1-C3H7Br. For CH2ClBr, the range in the ODP value is due to uncertainties in the magnitude of its loss to the oceans,

Since the time of the prior analyses, the two-dimensional model has been extensively revised and updated. The most important changes include:

-the chemistry and kinetic rates updated to the latest NASA recommendations (DeMore et al., 1997);

-the treatment of advective and eddy transport processes revised to better account for tropospheric and stratospheric transport compared to atmospheric tracers;

-tropospheric chemistry improved by improved representation of hydrocarbon chemistry;

-parameterization of tropospheric convective transport processes now included; improved representation of polar stratospheric clouds and ozone hole processes;

-improved treatment of latent heat effects on radiative derivation of atmospheric dynamics.

These changes have a significant impact on the derived ODPs for CH2ClBr and 1-C3H7Br. Of particular importance are the many changes made to the tropospheric chemistry and transport processes in the model.

As mentioned in the previous paper, ODPs are generally normalized to a CFC-11 lifetime of 50 years, and to an OH-driven methyl chloroform (CH3CCl3) partial lifetime of 5.9 years based on WMO (1995). The CFC-11 and CH3CCl3 scaling accounts for uncertainties associated with determining the Cl and OH distributions in the model. However, as shown in Wuebbles et at (1998), the measurements by Prinn et al, (1995) suggest that the best partial lifetime for reaction of CH3CCl3 with tropospheric OH is now thought to be 5.7 years. In this paper, we will present the ODPs based on both normalizations but will recommend that 5.7 years be considered as the standard.

The new version of the model now gives an atmospheric lifetime of CFC-11 of 49.3 years (as compared to 57 years in the prior model) and a partial lifetime for reaction of CH3CCl3 with tropospheric OH of 4.8 years (as compared to 8.1 years in the prior version). There are several reasons for the better comparison, including the improvements in transport processes, faster production of excited oxygen from ozone photolysis, and inclusion of hydrocarbon chemistry. As a result there is much less scaling of the final lifetimes and ODPs for CH2ClBr and 1-C3H7Br than in the previous version of the model.

Abstract  A three-dimensional chemical transport model has been used to investigate factors affecting the potential impact of a short-lived bromine compound on lower stratospheric ozone. The model is used to calculate the ozone depletion potential (ODP) of 1-bromopropane employing a previously used empirical approach, which depends on the lifetime of the compound and the amount reaching the stratosphere. We show that this approach may be unsuitable for very short-lived compounds. Indeed for a short-lived compound the definition of the lifetime itself is ambiguous. The lifetime varies with season, region of emission, and depends on the method of calculation. A series of tracer experiments reveals that the amount of bromine reaching the stratosphere, and hence the calculated ODP, can also be highly dependent on the distribution of the surface emissions. Where emissions are located solely in the equatorial region, the calculated ODP is over 3 times greater than when the emissions are centered over Europe. Vigorous convection in the tropics can lift the compound rapidly into the lower stratosphere where the bromine can be released and contribute to ozone destruction. For surface releases at higher latitudes the lifetime in the troposphere is significant compared with the time to reach the stratosphere and a smaller ODP is calculated. This highlights a problem in calculating ODPs for short-lived species. Uncertainties in the degradation mechanisms for short-lived compounds, and the subsequent fate of the degradation intermediates, add further uncertainty to calculations of their impact on the stratosphere. Additional methods need to be developed to assess their potential impact on the stratosphere.

Abstract  The National Toxicology Program (NTP) Center for the Evaluation of Risks to Human Reproduction (CERHR) conducted an evaluation of the potential for 1-bromopropane to cause adverse effects on reproduction and development in humans. 1-Bromopropane was selected for evaluation due to recent consideration of 1-bromopropane as a replacement chemical for hydrochlorofluorocarbons and chlorinated solvents. 1-Bromopropane is used in spray adhesives and in cleaning metal and electronic components; as a solvent for fats, waxes, or resins; and as an intermediate in the synthesis of pharmaceuticals, insecticides, quaternary ammonium compounds, flavors, or fragrances. The results of this evaluation on 1-brompropane are published in a NTP-CERHR monograph which includes: 1) the NTP Brief, 2) the Expert Panel Report on the Reproductive and Developmental Toxicity of 1-Bromopropane, and 3) public comments received on the Expert Panel Report. As stated in the NTP Brief, the NTP reached the following conclusions regarding the possible effects of exposure to 1-bromopropane on human development and reproduction. No data were available on 1-bromopropane exposures in the general US population. Therefore, conclusions were based on the available occupational exposure data and on studies in humans and laboratory animals. First, there is serious concern for reproductive and developmental effects at the upper end of the human occupational exposure range (18-381 ppm). Adverse developmental and/or reproductive effects have been reported in animal studies at exposure levels of >/=200 ppm. Second, there is minimal concern for reproductive and developmental effects when humans are exposed at the lower end of the human occupational exposure range (0.04-0.63 ppm). This level is at least 300- fold lower than the no effect level identified from reproductive studies in laboratory animals. These conclusions are based upon limited occupational inhalation exposure data. It is likely that worker exposures also occur through dermal contact with 1-bromopropane. However, no information was available on dermal exposures. NTP-CERHR monographs are transmitted to federal and state agencies, interested parties, and the public and are available in electronic PDF format on the CERHR web site (http://cerhr.niehs.nih.gov) and in printed text or CD-ROM from the CERHR (National Institute of Environmental Health Sciences, P.O. Box 12233, MD EC-32, Research Triangle Park, NC; fax: 919-316-4511).

Abstract  1-Bromo-propane (1-BP) is a replacement for high-end chlorofluorocarbon (HCFC) solvents. Its reaction rate constant with the OH radical is, on a weight basis, significantly less than that of ethane. However, the overall smog formation chemistry of 1-BP appears to be very unusual compared with typical volatile organic compounds (VOCs) and relatively complex because of the presence of bromine. In smog chamber experiments, 1-BP initially shows a faster ozone build-up than what would be expected from ethane, but the secondary products containing bromine tend to destroy ozone such that 1-BP can have a net overall negative reactivity. Alternative sets of reactions are offered to explain this unusual behavior. Follow-up studies are suggested to resolve the chemistry. Using one set of bromine-related reactions in a photochemical grid model shows that 1-BP would be less reactive toward peak ozone formation than ethane with a trend toward even lower ozone impacts in the future.

Abstract  Chlorobromomethane (CH2CIBr) and 1-bromo-propane (CH2BrCH2CH3 or simplified as 1 - CH3H7Br) are being considered for use as solvents and potentially in other applications. As with other chemicals that contain chlorine and/or bromine, it is important to determine the potential environmental effect from use and emissions of such compounds, including effects on stratospheric ozone. In this paper, the Ozone Depletion Potentials (ODPs), an important measure of the potential effects on ozone, are evaluated for these two compounds using our two-dimensional chemical-transport model of the troposphere and stratosphere. This is the first time these compounds have, to our knowledge, been evaluated with atmospheric models. Our model results show that the main removal process (ca. 99%) in the atmosphere for these compounds is the reaction with OH radicals. Photolysis has only a minor (⩽ 1 %) effect on the atmospheric lifetimes of either compound. The atmospheric lifetimes of CH2ClBr and 1 - C3H7Br due to atmospheric reactions are evaluated to be 0.40 yr (146 d) and 0.03 y (11 d), respectively. However, oceanic losses are likely to be important for CH2ClBr. Because of limited data on solubility and degradation in sea water, the lifetime for ocean loss currently has a range of 0.43-0.65 yr. This results in a total lifetime for CH2CIBr of 0.21-0.25 yr. An ocean sink for 1 - C3H7Br is likely to have an insignificant effect on its atmospheric lifetime or ODP. The ODP for 1 - C3H7Br is evaluated to be 0.006, while the ODP for CH2 ClBr including the effects of the ocean sink is 0.11–0.13. There are additional uncertainties in these values due to ambiguities in measured reaction rates and in the model treatment of atmospheric processes.

Abstract  Vapor-liquid equilibrium at 101.3 kPa has been determined for the title systems. The data were correlated by the Redlich-Kister and Wisniak-Tamir equations, and the appropriate parameters are reported. The activity coefficients of the ternary systems can be predicted from those of the pertinent binary systems. No ternary azeotrope is present.