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3 Summary of Health Risks As part of the Remedial Investiga- to an amount of the material known drinking,bathing in,or breathing tion,LLNL conducted a Baseline or suspected to cause harm. The vapors while showering in contam- Public Health Assessment to estimate risk is expressed as the chance of a inated ground water. the current and future risks to disease or an effect occurring. For Using EPA methods,LLNL esti- human health and the environment example,a risk level of one in one mated the potential cancer risks for if no cleanup actions were taken at million means that a person coming two different exposure scenarios,one LLNL. Copies of this assessment into contact with a certain chemical more conservative than the other: are available for review in the infor- would increase his or her normal mation repositories listed on the risk of developing cancer(which for ■ A "best-estimate" case,which back page. Americans is about a one in four took into account the locations of What is a Risk Assessment? chance)by one in one million. existing private and municipal sup- A risk assessment is a scientific Risk assessments make conserva- ply wells and the most realistichydrogeologic and chemical- procedure that uses facts and five assumptions that weigh in favor concentration estimates. The best- assumptions to estimate the poten- of protecting public health. For estimate scenario represents the tial for adverse effects on human example,the risk assessment for most probable set of conditions, health from exposure to chemicals. LLNL assumed exposure to the using EPA's assumptions regarding Potential risk is determined by maximum possible chemical concen- exposure and toxicity. assessing the amount of a material a trations,every day,for a 70-year person may ingest or come into con- period,even though actual exposure ■ A"health-conservative"case, tact with in water,soil,and air,and is likely to be far less. which assumes the highest conceiv- comparing the estimated exposure Results for LLNL able exposures,such as drinking two liters of water a day from the most Background ContinuedJrompugel The main ways that a person contaminated zone located immedi- could potentially be exposed to atel west of LLNL. cleanup alternatives for LLNL.This Livermore site contaminants is by y Feasibility Study(FS)evaluated the continued on page 4 health impacts after cleanup and esti- TRITIUM mated the costs of the cleanup alter- natives.(See the back page of this To date,tritium is the only radioactive material that has been found at or fact sheet for information on how near regulatory cleanup limits in ground water or soil at the LLNL site. you can review a copy of the FS.) With the exception of two monitor wells in the area of an old hazardous waste disposal pit in eastern LLNL,tritium has historically been found in LLNL has been conducting two ground water in concentrations well below the drinking water standard of pilot studies to test the effectiveness 20,000 picocuries per liter. of promising technologies for LLNL conducted a special risk analysis to assess the risks from tritium in extracting and,treating VOCs and ground water and soil at the LLNL main site. There are two primary ways FHCs from ground water and unsat- that someone could potentially be exposed to subsurface tritium at LLNL: urated soil.LLNL has extracted over 0 From air emissions associated with ground water cleanup activities 30 million gallons of ground water that,in the future,might be treating ground water that from the southwest part of the site contains both VOCs and tritium(e.g.,using an air stripping process). and employed an ultraviolet ■ From vegetation that has absorbed soil moisture and then given off into light/hydrogen peroxide system to the air the water that contains tritium. This process is called transpiration. destroy the contaminants.(See page The results of this screening-level risk analysis show that the maximum 7 for a description of this technolo- annual dose that a person could receive from either of these ways is substan- gy.)To conserve local ground water, tially lower than the 10 millirems per year dose considered to be safe under most of this treated water has been EPA's Clean Air Act. returned to ground water via a Studies show that the tritium in the subsurface at LLNL is moving so slow- recharge basin just south of LLNL, ly that,even if no cleanup were done,it will naturally decay to background or used at LLNL for landscape irri- levels before anyone offsite could be exposed to it in the future. At the pre- gation and in cooling towers.In sent,there are no known significant ongoing sources of tritium to ground another pilot study,the equivalent of water or the unsaturated soils. Consequently,tritium does not pose a health about 2,200 gallons of FHCs have threat. LLNL believes that it knows the major sources of tritium in the soils been removed as of June 1991 by and ground water,but will continue to monitor and investigate for tritium in withdrawing vapors from the unsat- the future. urated sediments in the Gasoline Spill Area.The FHC vapors were destroyed by a thermal oxidizer.