Air-water exchange of anthropogenic and natural organohalogens on International Polar Year (IPY) expeditions in the Canadian Arctic.

Shipboard measurements of organohalogen compounds in air and surface seawater were conducted in the Canadian Arctic in 2007-2008. Study areas included the Labrador Sea, Hudson Bay, and the southern Beaufort Sea. High volume air samples were collected at deck level (6 m), while low volume samples were taken at 1 and 15 m above the water or ice surface. Water samples were taken within 7 m. Water concentration ranges (pg L(-1)) were as follows: α-hexachlorocyclohexane (α-HCH) 465-1013, γ-HCH 150-254, hexachlorobenzene (HCB) 4.0-6.4, 2,4-dibromoanisole (DBA) 8.5-38, and 2,4,6-tribromoanisole (TBA) 4.7-163. Air concentration ranges (pg m(-3)) were as follows: α-HCH 7.5-48, γ-HCH 2.1-7.7, HCB 48-71, DBA 4.8-25, and TBA 6.4 - 39. Fugacity gradients predicted net deposition of HCB in all areas, while exchange directions varied for the other chemicals by season and locations. Net evasion of α-HCH from Hudson Bay and the Beaufort Sea during open water conditions was shown by air concentrations that averaged 14% higher at 1 m than 15 m. No significant difference between the two heights was found over ice cover. The α-HCH in air over the Beaufort Sea was racemic in winter (mean enantiomer fraction, EF = 0.504 ± 0.008) and nonracemic in late spring-early summer (mean EF = 0.476 ± 0.010). This decrease in EF was accompanied by a rise in air concentrations due to volatilization of nonracemic α-HCH from surface water (EF = 0.457 ± 0.019). Fluxes of chemicals during the southern Beaufort Sea open water season (i.e., Leg 9) were estimated using the Whitman two-film model, where volatilization fluxes are positive and deposition fluxes are negative. The means ± SD (and ranges) of net fluxes (ng m(-2) d(-1)) were as follows: α-HCH 6.8 ± 3.2 (2.7-13), γ-HCH 0.76 ± 0.40 (0.26-1.4), HCB -9.6 ± 2.7 (-6.1 to -15), DBA 1.2 ± 0.69 (0.04-2.0), and TBA 0.46 ± 1.1 ng m(-2) d(-1) (-1.6 to 2.0).

Overview--Air Force policy on halons.

Halons have been used for decades by the Air Force for a variety of fire protection applications. Their unique combination of effectiveness, low toxicity, ease of use, cleanliness, and low manufacturing cost appear to make them ideal for many situations. Unfortunately, they also deplete the earth's protective ozone layer and, consequently, their production is being phased out globally under the Montreal Protocol. United States legislation implementing the terms of the Protocol required an end to production of ozone depleting chemicals (ODCs) by the year 2000. In November 1991, the Air Force issued a policy requiring an end to ODC purchases by the end of 1997. In February 1992, President Bush announced an even more accelerated phaseout to 1995. The Montreal Protocol is expected to be amended to reflect the more aggressive US phaseout date. This accelerated date increases the urgency of the Air Force's search for ODC alternatives, especially for mission critical uses for which no alternatives have yet been identified. The search is complicated by the fact that the requirements an alternative must meet are unique to their specific application. This paper will provide an overview of the most important Air Force halon uses and review Air Force strategies for ensuring mission continuity until alternatives can be developed.

Human health and environmental toxicity issues for evaluation of halon replacements.

The Clean Air Act Amendments of 1990 require the US Environmental Protection Agency (EPA) to phase out production and use of ozone-depleting chemicals--among them, the fire suppressants, halons. As part of its rulemaking efforts EPA must evaluate the potential hazards to human health and the environment that could result from exposure to compounds that may substitute for halons. The EPA bases health hazard assessment on data obtained in studies involving short-term and long-term exposures. The former are used to evaluate potential risks of acute or delayed effects potentially resulting from short exposures at high concentrations, such as might be experienced in episodic emissions in the workplace. Studies with long-term exposure are used to assess potential adverse effects from continued exposure to low ambient concentrations. In addition, reproductive and developmental hazards are evaluated in several animal species. About ten chlorinated-, brominated-, and/or fluorinated-hydrogen-containing hydrocarbons, to be used alone or in combination, have been proposed as halon substitutes. In addition to health and safety, environmental, efficacy, and marketability considerations (Table I) need to be addressed for the selection of proposed halon substitutes. This presentation will discuss current EPA/Office of Air and Radiation thinking on a decision-tree approach for testing the toxicity of halon substitutes under the Significant New Alternatives Policy program.

Air Force approach to risk assessment for halon replacements.

Finding safe, environmentally acceptable, and effective replacements for Halon fire-extinguishing agents and other chemicals banned by the Montreal Protocol is a formidable task for Air Force research and development organizations. One factor that makes this task a challenge is the uncertainty in relating toxicology studies in laboratory animals to the human situation. This uncertainty from toxicology studies affects the risk assessment process by calling for very conservative decisions. Because of this uncertainty, public pressure and politics also impact the regulatory process. The Air Force approach to assessing health hazards for Halon replacements is to provide scientific information that directly applies to the parts of the extrapolation process that are responsible for the most uncertainty. Most regulatory agencies readily incorporate scientific information, when it is available, which can reduce uncertainty. These Air Force studies will be used to provide realistic exposure levels for replacement chemicals which will allow mission accomplishment and provide safety for the worker and the populace.

Pesticide pollution control. Suggestions are made for improving the quality of water subject to pollution by pesticides.

The suggested methods for evaluating water quality with respect to its content of selected groups of pesticides are based on interpretation of generally available information. They are intended to provide a base for discussion leading to the development of public policy for the inclusion of such values in water quality standards.