Under section 112(n)(6) of the Clean Air Act of 1990, as amended, Congress required EPA to carry out a study of hydrofluoric acid (also called hydrogen fluoride (HF)), to identify potential hazards to public health and the environment considering a range of events including worst-case accidental releases, and to make recommendations for reducing the hazards, if appropriate. This report, developed in response to the Congressional mandate, identifies and evaluates the hazards to the public posed by the production and use of HF. It is not intended to quantify risk to the public from HF. Analysis of public exposure to routine emissions was not included in this study because the statutory language focuses on worst-case releases from accidents. EPA Is submitting this report to Congress in fulfillment of Section 112(n)(6) of the Clean Air Act as amended.
Summary Findings and Recommendations
HF is used Industrially in large quantities throughout the United States (over 200,000 tons per year) and In a great number of applications across a broad range of Industries (over 500 facilities). It serves as a major feedstock and source of the fluorine molecule for the production of fluorinated compounds. An accidental release of HF from one of these industrial facilities could have severe consequences. HF is toxic to humans, flora, and fauna In certain doses and can be lethal as demonstrated by documented workplace accidents. HF can travel significant distances downwind as a dense vapor and aerosol under certain accidental release conditions. Because HF can exist as an aerosol, the cloud can contain a substantially greater quantity of the chemical than otherwise would be the case. Thus, the potentially high concentration of HF In these dense vapor and aerosol clouds could pose a significant threat to the public, especially in those Instances where HF is handled at facilities located In densely populated areas. Prompt and specialized medical attention is necessary to treat HF exposure properly.
However, the risk to the public of exposure to HF is a function of both the potential consequences and the likelihood of occurrence of an accidental release: and the likelihood of an accidental release of HF can be kept low if facility owners/operators exercise the general duty and responsibility to design, operate, and maintain safe facilities. In particular, owners/operators can achieve an adequate margin of protection both for their workers and the surrounding community by assiduously applying existing industry standards and practices, existing regulations, and future guidance and regulations applicable to various classes of hazardous substances in various settings.
The properties that make HF a potentially serious hazard are found Individually or In combination in many other industrial chemicals; thus, HF does not require unique precautions. Instead, within each of the several different circumstances in which HF is handled, an appropriate combination of general and special precautions should result in: (1) the safe management of HF and other hazardous substances with an emphasis on accident prevention; (2) the preparedness to properly and quickly respond to chemical emergencies and to provide specialized medical treatment if necessary; and (3) community understanding of the risks Involved.
The EPA does not recommend legislative action from the Congress at this time to reduce the hazards associated with HF. The Agency believes that the legislative authorities already in place provide a solid framework for the prevention of accidental chemical releases and preparedness in the event that they occur. The Agency recommends that facilities handling HF coordinate closely with their Local Emergency Planning Committees (LEPCs). LEPCs and facilities that handle HF should conduct drills and exercises to test mitigation, response, and medical treatment for a simulated HF accident. Furthermore, the Agency recommends that facilities actively conduct outreach efforts to protect public health in the event of an accident, and that proper actions will be taken during an emergency. Facilities should be able to rapidly detect, mitigate, and respond to accidental releases in order to minimize the consequences (e.g., through detection, monitoring, mitigation, and alert or alarm systems). Finally, the EPA will continue to support research and development efforts for process safety improvements and implementation, modeling and assessment improvements, and accidental release monitoring and detection improvements.
Summary of Report
HF is a very corrosive and toxic inorganic acid. It can either be a gas or liquid in anhydrous form (without water; 100 percent HF) or in aqueous solution (with water). Exposure to HF can cause injury through inhalation, direct contact, or ingestion. HF is particularly caustic to tissue and exposure may require special treatment. HF is one of the more corrosive and toxic industrial chemicals, but it is not unique among hazardous chemicals; other inorganic acids are similarly corrosive (e.g., hydrochloric acid), and some other relatively common chemicals are similarly toxic or more toxic than HF (e.g., chlorine). HF boils at 67F, a temperature that is frequently exceeded under ambient conditions, Consequently, if HF liquid is released, it may vaporize under ambient conditions. HF exhibits release characteristics in some circumstances that may make it particularly hazardous to the public. HF molecules may associate with one another (i.e., form larger molecules like H4F4, H6F6, H8F8) via hydrogen bonding; such molecules may form a cloud that is heavier than air. A vapor cloud of single, unassociated HF molecules will be lighter than air. A cloud that is lighter than air is likely to disperse more readily than one that is heavier than air. In addition, if HF is released under pressure above its boiling point, droplets of HF may be carried into the air as aerosol along with HF vapor. Anhydrous HF released under pressure above its boiling point may form a cloud of vapor and aerosol that is heavier than air and that may travel for long distances close to the ground, posing a threat to people in its path. Although an HF vapor cloud may form under some conditions from a release of an aqueous solution of HF, depending on concentration and release temperature, anhydrous HF is much more likely to form a vapor cloud and, therefore, is potentially more hazardous to the public.
HF has been a focus of interest to industry for several years. Industry groups have carried out research and tests to characterize the behavior of HF upon release, improve dispersion modeling techniques, and to test systems for mitigation of HF releases. A large accidental release of HF at a petroleum refinery drew additional attention to the hazards of HF releases. The South Coast Air Quality Management District (SCAQMD) studied the hazards of HF use and production in the Los Angeles Basin and adopted regulations phasing out the use of anhydrous HF within the Basin. These regulations were litigated, during which time their implementation was suspended by the court. However, a recent court decision permitted implementation of the rule after additional rulemaking procedures are conducted.
HF is produced at three sites in the United States: Allied-Signal, in Geismar, Louisiana; DuPont Chemicals in La Porte, Texas; and Elf Atochem in Calvert City, Kentucky. Production capacity was approximately 206,000 tons in 1992. Both anhydrous and aqueous HF have a wide variety of uses. The largest use is the manufacture of fluorine-containing chemicals, particularly chlorofluorocarbons (CFCs). Fluorocarbon manufacture consumes 63 percent of the total HF used. HF also may be used as an alkylation catalyst for the production of gasoline blending components; this use consumes 7 percent of the total. Other uses include aluminum production (3 percent, with additional HF produced and used captively) and nuclear applications (5 percent). A number of other uses, including stainless steel pickling, manufacture of various chemical derivatives and products, electronics, specialty metal production, and glass etching and polishing, consume the remaining 22 percent of HF produced.
HF is regulated under a number of U.S. statutes. It is listed as a hazardous substance under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), as a hazardous waste under the Resource Conservation and Recovery Act (RCRA), as an extremely hazardous substance under section 302 of the Emergency Planning and Community Right-to-Know Act (EPCRA), as a toxic substance under EPCRA section 313, as a hazardous material in transportation under Department of Transportation regulations, as an air contaminant under the Occupational Safety and Health Act (OSHA) Air Contaminants Standard, and as a highly hazardous chemical under the OSHA Process Safety Management Standard. HF has been proposed as a regulated substance for accidental release prevention under section 112(r) of the Clean Air Act. HF is subject to risk management programs in several states, including California, Delaware, Nevada and New Jersey. All of these regulations include HF as one of a number of regulated substances. The South Coast Air Quality Management District in the Los Angeles Basin is the only government agency that has adopted specific regulations for HF; these regulations would phase out use of anhydrous HF, would require interim control measures, and would impose reporting and inventory requirements. Industry has taken steps specifically to address and minimize the hazards of HF use and production. The American Petroleum Institute (API), the major trade association of the petroleum industry, has developed recommended practices for operating and maintaining HF alkylation units at refineries; the procedures and practices described are intended to minimize the potential for an HF release, mitigate the effects of a release if it occurs, and provide for oversight and audit of the entire process. The National Petroleum Refiners Association endorses the API recommended practice. The Chemical Manufacturers Association (CMA) sponsors an HF Mutual Aid Group comprised of specially trained teams that respond to emergencies involving HF. Companies that produce and use HF have also formed an HF Panel under CMA auspices. The purpose of the panel is to make safety, health, and environmental information available to the entire industry. The panel appoints various Task Groups to address aspects of HF safety, and develops and maintains guidelines for the safe handling of HF.
In the process of conducting the study and gathering information about HF, EPA visited a number of facilities that produce or use HF and observed the procedures used to promote process safety. These procedures include designing equipment for HF use to minimize hazards; regularly testing, inspecting, and maintaining equipment; and training workers. Some facilities have installed HF detection systems; however, reliable and accurate HF detectors have been difficult to develop, particularly for perimeter monitoring. A number of facilities also have mitigation systems to reduce the quantity or concentration of HF if a release occurs. Systems include water spray systems to knock down HF vapors in case of a release, scrubber systems to absorb HF vented from process streams, and emergency de-inventory systems to rapidly move HF from failed equipment to safe equipment.
Facilities also use remotely-operated emergency isolation valves to prevent and mitigate releases. Because EPA observed practices only at selected sites, it is not clear to what extent practices to promote HF safety are used at HF facilities in all industry segments, Special equipment is used in transportation to prevent releases in case of a transportation accident. U.S. HF producers transport anhydrous HF in rail cars that exceed DOT safety requirements and have headshields and shelf couplers to protect the tanks in the event of a derailment. Safety relief valves on tank cars and trucks are used to release HF gas in the event of overpressurization. These valves are protected by extra heavy rollover type domes. Valves for loading and unloading are also contained within the rollover protection dome on the top of the tanks. HF producers provide rigorous training programs for drivers of HF vehicles. They also may conduct route risk analysis. One HF producer has installed a satellite tracking system to track HF trucks. Loading and unloading of HF from transport containers is often cited as a point where a release could occur, particularly as a result of failure of a transfer hose. To prevent releases, specially designed transfer hoses are used, and precautions are taken to prevent corrosion of piping, valves, and vessels.
A large release of HF from a refinery in 1987 led to formation of a vapor cloud that migrated through a residential area, causing a number of injuries, a large-scale evacuation, and damage to vegetation. In general, however, there have been relatively few reports of accidents involving HF, and only a small fraction of these caused impact to the public. There have been no off-site deaths repotted from HF releases although some worker deaths have occurred. EPA’s analysis of accident data is consistent with the expectation that releases of anhydrous HF or concentrated aqueous HF solution (70 percent HF) pose more hazards both on-site and off-site than less concentrated aqueous HF.
For its analysis of the hazards to the public from HF, EPA carried out consequence analysis, using computer modeling techniques, for a range of worst-case accident scenarios. Modeling indicated that releases of large quantities of HF over a short period of time (e.g., resulting from catastrophic vessel failure) could pose a hazard to people far beyond facility boundaries, particularly under low wind speeds and stable atmospheric conditions. This type of accident is highly unlikely, but, based on modeling results, has the potential to cause great harm. Smaller releases may or may not pose a hazard beyond a facility fenceline depending on the circumstances of the release.
Mitigation systems (e.g., water spray, emergency de-inventory, automatic shutoff valves) were also modeled and shown to reduce affected distances downwind. EPA did not consider the probability involved with these worst-case accident scenarios. While visiting HF facilities to observe management practices, EPA also gathered information on the Interaction between communities and facilities for emergency preparedness and planning. In the event of a release of HF, coordination between the community and the facility would help community officials react quickly and take proper actions to protect the public. EPCRA (SARA Title Ill), mandated the formation of Local Emergency Planning Committees (LEPCs) to develop emergency response plans for chemical accidents. Some HF facilities are members or supporters of LEPCs. HF facilities in some industries have established mutual aid agreements that may also involve community officials.
Some HF facilities cooperate with local government agencies in activities such as conducting emergency drills. The Chemical Manufacturers Association (CMA) has developed a community oriented program called the Community Awareness Emergency Response (CAER) program which recommends ways for chemical facilities to develop working relationships with communities to address emergency situations involving many chemicals including HF. EPA’s observations indicated that in some areas near HF facilities, the public has not shown much concern or interest in the hazards of HF and other chemicals, or in emergency preparedness and planning for chemical accidents. Also, some facilities acknowledge that facility outreach can be greatly improved.
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