The Role of Field Testing in Environmental Measurements
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lmost two years ago, I attended a workshop on environmental testing sponsored by a trade association representing commercial laboratories. The keynote speaker, selected because his name is widely recognized, described environmental-testing laboratories as dinosaurs. They would all be out of business in a few years, he said, and field testing was the way of the future. Environmentaltesting businesses that didn’t understand this simple axiom were doomed. As you might guess, this created quite a stir, especially among the “doomed” commercial laboratories. Representatives of several commercial labs asked me: “He can’t be serious, can he?” I told them he seemed pretty serious to me. The question now is, Was he right? To answer this question, I asked several industry experts whether commercial laboratories’ sales were declining and whether sales by companies that manufacture fieldmeasurement systems and kits were increasing. Their evaluations were fairly consistent: The rate of growth in the industry has slowed dramatically over the past four years, from a high of about 15% per year down to 2-4%. The experts believe this trend will continue. During the same time, companies manufacturing field test equipment grew an average of about 15% per year. Although these experts concede that more testing is being done in the field, they don’t foresee the dra-
matic changes predicted by the keynote speaker. This information does not demonstrate a decline in commercial laboratory testing in an absolute sense; however, one might argue that the slowdown in laboratory growth coupled with growth in field testing tends to support the keynote speaker’s position. Based on the discussions I’ve had with industry experts, test kit manufacturers, and environmental project
Environmentaltesting laboratories have been
. .
I managers, I think it‘s fair to say that field testing is not having a major effect on testing performed by fixed laboratories-at least not yet. I think it’s also fair to say that field testing is playing a role in environmental testing, and this role will likely increase over time. This poses a more fundamental question: What is the role of field testing in environmental measurements? The following analysis was de-
536 A Environ. Sci. Technol.. Vol. 28, No. 12. 1994
veloped through discussions with several environmental project managers who have used testing approaches ranging from simple test kits to sophisticated mobile laboratories. When should you do field testing? The first consideration is time. You have to ask when are you going to use the data. Don’t confuse this with when you wont the data. The issue is when you can actually put the data to use. If the answer is anything less than a day or two, then field testing is definitely worth considering. In other words, field testing is valuable if the time it takes to obtain the data roughly equals the time necessary to take the next step in your field process. For example, let’s suppose a well is being drilled in search of a contamination plume. The drilling rate is about 10 ftlh and you don’t want to drill deeper than necessary. Furthermore, you don’t want the drill rig to be idle while you wait to find out whether further drilling is required. The time frame for the decision is about an hour. If you could get test results in that time you can maximize the efficiency of the drilling operation while ensuring that you don’t drill deeper than necessary. (In reality, you’d probably want to drill a little deeper after hitting the plume anyway, but you can see how the logic applies.) The same logic can apply to most removal actions. A test that can be done in a time frame complementary to your operation can maximize your efficiency. Because field tests can give results within a few minutes to a few hours, they are a sensible approach. The next major consideration is whether the question you are trying to answer is compatible with field testing. Field measurements are best suited to providing yesho answers about a single analyte or group of related analytes. This is a
001 3-936X194/0927-536A$04.50/0 0 1994 American Chemical Society
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result partly of the nature of the tests and the field environment. Many field tests are available in kit form and designed to give yedno answers about a user-defined concentration [e.g., is the concentration of total petroleum hydrocarbons (TPH) > 100 mg/L?l Using the well-drilling example, suppose you decide that a concentration of TPH > 100 mglL would constitute hitting the plume. You then monitor the results to see whether any samples exceed the 100 mg/L threshold by using a test kit for TPH that covers the 100-ppm range. The question is in a yeslno form. This situation is ideal for a field testing application. If there is no immediate use for the data, then field testing offers no real advantage over testing in a laboratory. Nor is field testing advantageous when the information required involves many analytes, that is, when the requirement is to determine more than two or three metals or more than a few organic compounds or classes.
Are field tests reliable? The answer is generally yes, but it depends on how one judges reliability. If a threshold is established and the question is whether the measured concentration is above or below the threshold, then testing in the field, whether using test kits or mobile laboratories, is very reliable. Typically, false positive errors are less than 5% and false negatives even less than that. By factoring this reliability into your decision criteria, field tests can result in extremely reliable decisions. Of course, the reliability of a given test at a specific site will vary. Most environmental managers get around this problem by first evaluating a few samples from the site using the anticipated field test while sending splits to a fixed laboratory. If the results show the tests are comparable, then the field test should produce reliable results. During field testing, it's a good practice to send a portion of the samples to a fixed laboratory as part of your quality assurance program. Moreover, many field-testing plans use fixed laboratories to verify the more contaminated samples and send them off site for more in-depth analysis. The key point is that field testing provides a certain level of confidence. Resourceful program managers use these tests in ways that maximize utility by establishing
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What about regulatory acceptance? Questions that always come u p are, Is this an approved method? and Will regulators accept the results? The answers are “no” and “sometimes,” respectively. EPA has not yet approved the use of fieldtesting kits such as immunoassays. However, some EPA offices are planning to accept them and, interestingly enough, some EPA laboratories and offices use them now. (EPA often doesn’t follow its own rules.) For those professionals considering using a field method, an approach I’ve seen used successfully in several EPA regions is to simply inform the region and state regulatory authorities that you intend to use the field method as part of your project. Explain how it will be used, the decisions you intend to make, and how you will assure validity. If EPA and the state do not object, use the method according to your plan. If they do object or want additional assurance, you might be able to negotiate a more extensive quality assurance program to address their concerns and still meet your requirements. If that fails, and you still want to pursue field testing, you might enlist the support of one of EPA’s own laboratories that are using the test. The company that supplies the test can give you a list of contacts. Does field testing save money? Testing in the field, if used properly, can save on overall project costs, assuming that the project capitalizes on yeslno decisions in relatively short time frames and does not require a long list of analytes. If you’ve done a good job at matching the field test with time and analytes, you can typically save 50% or more on testing alone. You may also realize savings from faster remediation. However, this will vary by project. What about mobile laboratories? A number of project managers tell horror stories about using mobile labs, They cite problems in keeping the mobile lab adequately staffed and supplied, and point out that utilization rates are less than 10%. Because of these problems, these managers claim that field labs almost always end up permanently parked outside a fixed laboratory and therefore aren’t worth the effort.
I have found two common problems that may be the cause of such negative experiences. The mobile laboratories used were designed to offer the same analytical services as a fixed laboratory, and the services provided d i d not match t h e project's specific requirements. In contrast, managers who had positive experiences with mobile labs typically say that the lab they used was configured specifically for their project. It contained the right analytical equipment and did not include instrumentation or equipment that wasn't used frequently. The mobile lab was configured to provide only the measurements required for field decisions.
Conclusions Environmental project managers are increasing their use of field testing because projects can be completed faster and cheaper. Field testing does not replace fixed laboratory testing. It does, however, offer a cost-effective alternative for many projects. If you are considering field testing, keep the following points in mind: The data developed in the field must have an immediate use. If you can't identify an immediate use, there is no real advantage to performing the measurements in the field. Field measurement techniques should cover only the analytes needed for the immediate decision. The sensitivity of the measurements must cover the decision point. To determine their reliability, test field measurement techniques on samples from the site before using them for your project. Some techniques may suffer from interferences present at the site. Check with regulators before using field measurements to make sure they have no objections. If they object, negotiate. Before using a mobile laboratory, make sure it is configured specifically for your project. If the laboratory contains excess equipment or is sized beyond your needs, don't use it. Jomes Poppiti earned o Ph.D. in chemistry from George Washington University. He has worked for the Food ond Drug Administration, EPA, and Finnigan MAT. He now works on the Department of Energy's Tank Waste Remediotion Progmm for the Hanford, Washington, site.
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