|  | Quick Facts about PDPSampling OperationsLaboratory OperationsDatabase/Reporting
HistoryPDP was started by USDA in May 1991 to provide data on pesticide dietary    exposure, food consumption, and pesticide usage.PDP    has tested about 40 different commodities:      fresh/frozen/canned fruit & vegetables, fruit juices, whole milk, grain, and    corn syrup.PDP    has tested for more than 160 different pesticides:      insecticides, fungicides, herbicides, and growth regulators.

Sampling OperationsPDP samples are collected by 10 participating    States, which represent****about **50 percent** of the Nation's population and    all regions of the country.Samples    are collected **close to the point of consumption**, at terminal markets and    large chain store distribution centers.  This allows the capture of sample    identity data, takes into account pesticide degradation during transit and    storage, and provides data on residues resulting from postharvest applications of    fungicides and growth regulators.**Sample    sizes** for all fresh fruit & vegetables are 5 lbs.; processed products are 3 lbs.;    milk, corn syrup, and juices are 1 quart; and grains are 500 grams.For    some commodities (such as grains), **Federal personnel** perform sample collection    because of access and expertise in collecting, packaging, and shipping certain products.The    number of samples to be collected is **apportioned** according to State **population**    or commodity **production** figures.Samples    are **randomly chosen** without regard for commodity origin or variety.  Samples    reflect what is typically available to the consumer thoughout the year.PDP's    statistically-reliable sampling protocol is designed to select random samples that best    represent pesticide residues in the food supply to allow for **realistic estimates** of    **exposure** to these chemicals.All    States, except California, **transship samples** to a single laboratory for dedicated    commodity analysis.PDP    maintains Standard Operating Procedures (SOPs) that are designed to    provide criteria to State samplers for site selection and specific instructions for sample    selection, shipping, and handling.

Support    and oversight for all sampling operations is provided by USDA's National Agricultural    Statistics Service (NASS).Detailed    information about PDP sampling operations can be found in Section II of the PDP 1998 Annual Summary Report.

Laboratory OperationsAnalytical services for PDP are provided by 8    State and 3 Federal laboratories.      Participation as a contributing laboratory is **voluntary** and is funded    through a  Cooperative Agreement between the laboratory and USDA.Upon    receipt, samples are visually **examined** for acceptability and are **discarded**    if determined to be inedible (decayed, extensively bruised, or spoiled).Accepted    samples are prepared (washed with inedibles removed) **emulating****consumer****practices**.      All sample preparations are controlled by program-wide Standard    Operating Procedures (SOPs) that **ensure consistency**    between laboratories.Samples    are mixed or **homogenized** into one representative (composite) homogenate.

PDP    also conducts special surveys on **single-serving** sized food items to support acute    dietary risk exposure studies.

Residues    are isolated from sample homogenates using various extraction    and clean-up procedures.  Extracts representing the initial sample are then ready    for instrumental analysis. PDP    Laboratories continuously evaluate and utilize one or more state-of-the-art instrumental    systems when conducting initial identification and    quantitation of pesticides.

All    extraction **methods** and **instrumental systems** employed are independently **validated**by the laboratory performing the analysis.

PDP    requires continuous **quality assurance** (QA) controls and on-site monitoring by    independent QA officers to ensure the reliability of PDP data. Performance**equivalency**    of the participating laboratories is monitored by a program-wide check-sample program.All    **residues** initially identified are **verified** using various forms of mass    spectrometry, atomic emission detectors, or by alternate detection systems.PDP    laboratories also report **non-detects** for all pesticides screened, with    corresponding reference Limits of Detection (LOD).Detailed    information about PDP laboratory operations can be found in Section III of the PDP    1998 Annual Summary Report.

Database Management &    ReportingPDP maintains an **electronic database** which serves as a central    repository for its residue monitoring data.  The data captured and stored in the PDP    database include product information, residue findings, and process control    recoveries for each sample collected and analyzed, plus fortification results for each set    of samples.Each    **calendar year** database is stored in a separate database structure, allowing for    easier administration and reporting of data.

PDP    utilizes a customized **software application** package that provides participating    laboratories with the ability to **enter the PDP data** into interactive data entry    screen and then to **electronically transmit** the data to the central office via    modem and standard telephone lines. Ad-hoc    queries and customized reports are generated in response to **data request**from government    agencies and the public sector. **Subsets**    of the PDP calendar year **databases** are made available for download    on this PDP Internet **Web site**. PDP    has published Annual Summary reports to present program    findings for calendar years 1991 through 1998. Detailed    information about PDP database management and reporting activities can be found in Section    IV of the PDP 1998 Annual Summary Report.
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