Re-entry studies

Field methods for performing farm worker exposure and re-entry studies... 

Preparing a detailed protocol according to GLP standards may be useful for researchers planning a worker exposure or re-entry study, even though the study may never be submitted to the EPA to support the registration of a pesticide product. Having a detailed protocol helps to solidify one s plans for the study, and assists in the documentation phase of the study. This documentation phase will be addressed in some detail later. 

One of the most important aspects of designing a successful worker exposure or re-entry study is the selection of the agricultural site at which to perform the study. One must first define the growing region in which the pesticide is to be used to the widest extent possible. This is important since this region would have the most farms, farmers, commercial applicators, or re-entry workers which would have work habits, equipment, and land, which would best represent the use of the product. 

One of the first items of importance when attempting to select an agricultural site at which to perform a worker exposure/re-entry study is to review the label on the product. Such a review will reveal the areas where the product is to be used and the conditions under which the product is to be applied. One should look for whether a product is to be applied by ground or air and if there are any restrictions as to the locations where the product is to be used. One must also pay attention to label directions concerning types of soil where the product is to be used since this could affect rates of use. 

The other type of site, which is less commonly used for worker exposure and/or re-entry studies, may be found on a research farm. These research farm facilities may... 

When planning a worker exposure/re-entry study, the number of sites selected should reflect the use pattern of the product. Usually three different sites, each in a different geographical location, are recommended to ensure good representation of the areas when the product has wide use. The different geographical locations offer the researcher diversity in equipment used to treat the crops as well as diversity in the work habits of the individuals in the study. 

Portable weather stations are useful to have available at the field laboratory for acquiring weather data during the course of the worker exposure/re-entry study. There are a variety of portable weather stations available from a variety of suppliers. Weather data to be collected are rainfall, wind direction, wind speed, air temperature, and relative humidity. These electronic weather stations will record the necessary weather parameters on a routine basis. The data are stored and can be transferred to a laptop computer or disk as desired by the Field Scientist. Such portable electronic weather stations are useful during the course of the dislodgeable residue portion of a worker re-entry study when dislodgeable residue samples are taken from remote test sites over the course of a 30-day period. 

The test substance may be acquired in a number of ways. One common method is to purchase the product from a chemical dealer. This method of acquiring the test substance for a worker exposure or re-entry study allows one to proceed rapidly with the execution of the field portion of the study without the serious delays encountered while waiting for a test substance to be manufactured, assayed, and shipped to the site. Although having a test substance formulation which has been assayed under GLP standards and for which a certificate of analysis has been shipped to the test site is desirable, there are several instances when this is not practical. For example, one may encounter a worker exposure study where the pesticide to be evaluated is sold only in mini-bulk or even large bulk quantities holding as much as 2000 gal. In this case, duplicate 5-10-g or 5-10-mL retainer samples should be taken from the bulk or mini-bulk tanks for assay after the worker exposure study is in progress. 

In many instances under GLP, the test substance may be manufactured and assayed for the specific purpose of use in a worker exposure or re-entry study. This is normally done when the amounts of the product to be used are relatively small, and the product is not sold in bulk. In this case, a certificate of analysis should be obtained prior to the initiation of the field portion of the smdy. In this case, the manufacturer should retain some of the material for periodic reassay to meet GLP requirements. 

Most consent forms that have been developed have at some time been reviewed by standing ethical review boards, usually associated with a university. The format of the consent form described above has been reviewed over time by more than one ethical review board and would be acceptable in most States for the purpose of acquiring the consent of potential volunteers in a worker exposure or re-entry study. If performing worker exposure studies in California, the researcher is advised to contact the State regulatory agencies and submit the draft consent form and study protocol to the State-appointed ethical review board for review and approval prior to initiation of the field phase of the study. Of course, if the researcher has any doubt about the acceptability of the proposed consent form, he/she should contact the appropriate state agencies where they plan to perform the study. 

Volunteers for a worker exposure or re-entry study should be selected with care and with confidentiality. The volunteer s privacy and also respect for the volunteer should be kept in mind during the field phase of the study. With all worker exposure/re-entry studies, the worker volunteer is the key to a successful study. 

Execution of the field portion of the worker exposure/re-entry study... 

Both inner and outer whole-body dosimeters are common tools to measure successfully dermal exposure to pesticide workers and are employed in a variety of ways in mixer-loader/applicator or re-entry studies. 

Such field-fortified matrix samples are absolutely necessary as a part of any worker exposure or re-entry study in order for the behavior of the active ingredient to be... 

In addition, the use of field fortification samples measures the carefulness factor of the Field Scientist during the field research and allows a Study Director/Manager or distant observer to obtain a quality control estimate on the field portion of the study. For this reason, the field fortification samples are usually meant to be different from laboratory procedural fortifications and are meant to be prepared under field conditions, which are considerably more rigorous than are controlled laboratory conditions. For example, environmental factors such as heat, humidity, wind, human stress, and other human factors such as fatigue to the Field Scientist are an integral part of any field worker exposure/re-entry study. Field fortifications made to matrices under these conditions will test and readily demonstrate the ability of the Field Scientist to perform such a difficult study under trying circumstances. 

Observations of the test subjects during the course of the field portion of the worker exposure or re-entry study are extremely important in order to interpret the data that are gathered at the field site and to interpret the final analytical data. There are two schools of thought when making observations of field workers during mixer-loader/applicator worker exposure or re-entry studies. 

Field data from a worker exposure and re-entry study can be organized many ways. Field data usually fit into several categories including activities and traits of workers... 

Many and varied field techniques involved in the planning, execution, and direction of the field portion of worker exposure and re-entry studies have been considered. Suffice it to say that there are many ways to perform such studies, and the important thing to remember is that good scientific thought and planning will produce an excellent study. The scientific validity of such studies should rest on the basic principles of science. There are various guidelines and protocols which may be followed for regulatory... 

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