exposure 2

Objective: Apply the concepts from the exposure assessment planning phase particularly the development of a working definition of exposure, selection of exposure indicators, and alignment with the exposure science continuum

Instructions: Based on the pesticide scenario and the pathway receptor diagram and conceptual site model provided on iCollege, complete the following tasks using the attached Word document. Be specific and concise.

1. Define true exposure for each subpopulation:

Using the provided scenario, diagram, and model, write a brief definition of true exposure for each of the target populations farm workers, nearby residents, and recreational users of downstream water bodies.

For each group, include (a) the exposure routes and environmental media involved, (b) acknowledgement of timing (acute and/or chronic), and any key assumptions about when, how, and how often exposures occurs.

1. Propose a measurement strategy:

Describe how you would measure exposure using environmental samples, surveys, or observation (indirect methods).

Your response should address what types of data you would collect (e.g., stationary air monitors, soil sampling, specific survey questions), and if relevant which environmental media you would sample and where sampling would occur.

1. Define measured exposure for each subpopulation:

Write a brief definition of measured exposure based on the strategy you proposed for each sub-population. Be explicit about what your measurements capture.

1. Exposure continuum placement and justification:

Based on the exposure science continuum, indicate where your selected measurement approach falls and justify your reasoning. If youre proposing multiple methods, you can describe how they span the continuum.

Tips:

• True exposure is often unobservable in practice it reflects what a person actually comes into contact with, at a biologically relevant point, over time.
• Measured exposure is what you can realistically capture through sampling or data collection.
• Consider whether each subpopulation is more likely to experience acute (short-term) or chronic (long-term) exposures and whether your measurement approach captures that.

Scenario: A large agricultural operation applies organophosphate pesticides to its crops using ground-based and aerial spraying. The farm is located near a small rural community. The area includes:

• Several farmworker housing units directly adjacent to the fields
• A small residential neighborhood located 1 mile downwind from the fields
• A stream running next to the fields that is used for irrigation and eventually flows into a recreational lake used for swimming and fishing about 5 miles downstream

Pesticide movement through air, soil, surface water, and biota should be considered. Exposure pathways may involve multiple environmental media and sources including direct application, pesticide drift, runoff, and accumulation in the environment.

The purpose of the exposure assessment is to evaluate the potential for both short-term (acute) and long-term (chronic) human exposures to organophosphate pesticides from ground-based and aerial spraying at a large agricultural operation. Focus potentially exposed populations include farm workers, nearby residents, and recreational users of downstream water bodies.

The goal of this exposure assessment is to identify and characterize exposure pathways to inform risk management and mitigation strategies. Be sure to consider the time scale of different exposure pathways and identify whether certain populations or pathways are more likely to result in acute versus chronic exposures.