PHLT 8702 Week 7 Field Quality Plan Example

Decided Before Any Pump Runs: A Field Quality Plan for Wood Dust and Formaldehyde Sampling at a Composite Furniture Plant, Covering Blanks, Flow Checks, Custody and Laboratory Requirements

Student Name

Walden University

PHLT 8702: Environmental and Occupational Exposure Measurement and Assessment

Instructor Name

Month Day, Year

Decided Before Any Pump Runs: A Field Quality Plan for Wood Dust and Formaldehyde Sampling at a Composite Furniture Plant, Covering Blanks, Flow Checks, Custody and Laboratory Requirements

Why a Field Quality Plan

A sampling result is only as good as the steps that produced it. A cassette weighed on a drifting balance, a pump whose flow sagged during the shift or a tube left on a warm dashboard can each change a number without leaving a visible trace. The plant's sampling program will produce about 76 inhalable dust samples and a set of formaldehyde samples over six weeks. This plan sets down, before the first pump runs, how each source of error will be prevented or detected and what happens to a sample that fails a check. The NIOSH sampling strategy manual makes the same point in general terms: decisions about sampling procedures and their documentation belong at the planning stage (National Institute for Occupational Safety and Health [NIOSH], 1977).

Blanks

Field Blanks

For every batch of samples sent to the laboratory, at least two field blanks, or 10% of samples if that is larger, will travel with the samples. A field blank is an unused cassette or tube that is taken to the plant, opened briefly in the sampling area as if it were being mounted, closed and returned with the real samples without any air drawn through it. Field blanks reveal contamination or weight change from handling, transport and storage.

Media Blanks

For formaldehyde, the laboratory will also analyze unopened tubes from the same lot, which detect formaldehyde already present in the sorbent. DNPH-coated media can pick up formaldehyde from the air of offices and vehicles, so tubes will be stored in sealed bags with their caps on until mounting.

What a Blank Result Triggers

If a field blank for wood dust shows a weight change larger than the laboratory's limit of detection, the batch will be reviewed and samples near the comparison limit will be flagged. Blank values will not be subtracted automatically; the laboratory's policy will be stated in the report, and a contaminated batch may be repeated.

Flow Checks

Each pump will be calibrated before and after every sample with a primary flow standard, using a representative cassette or tube in line. The IOM samplers are designed to run at 2.0 liters per minute, and the inhalable convention they follow depends on that flow. If the post-sampling flow differs from the pre-sampling flow by more than 5%, the sample will be marked and its volume calculated from the average; if it differs by more than 10%, the sample will be voided and the worker resampled on another randomly chosen day. Kenny et al. (1997) showed that inhalable sampler performance depends on how the sampler is used, so flow and orientation will be checked at midshift as well.

Field Records

A one-page form will accompany each sample, recording the worker's group and identifier, the pump and cassette numbers, start and stop times, flows, tasks observed, whether local exhaust was operating, the wood species and any unusual events. The hygienist will sign the form at the end of each shift. Records will be kept with the results so that a reviewer years from now can understand each number, unlike the unexplained sample that opened this course.

Chain of Custody

Samples will be labeled at the plant with a code that does not identify the worker by name. A custody form will list every sample and blank in the shipment and will be signed each time the package changes hands, from the hygienist to the courier to the laboratory receiving clerk. Formaldehyde tubes will be shipped cold and analyzed within the holding time specified by the method. A sample arriving with a broken seal, a missing label or a temperature excursion will be recorded as compromised and not reported as a valid result.

Laboratory Requirements

The plan requires a laboratory accredited for industrial hygiene analysis, using NIOSH Method 0500 or an equivalent gravimetric method adapted for IOM cassettes, which are weighed whole with their filters. Formaldehyde will be analyzed by NIOSH Method 2016. The laboratory will report limits of detection and quantitation for each batch, blank results and any deviations, and it will retain filters for six months in case reanalysis is needed.

Duplicates

On about one sampling day in ten, a second IOM sampler will be mounted beside the first on the same worker. Side-by-side results show how much two samplers in the same breathing zone disagree, which sets a floor on how small a difference between workers can be trusted. Harper et al. (2004) found that different samplers collect different wood dust masses, so all duplicates will use the same sampler type.

Training and Supervision

Only two people will mount, start and stop samplers: the plant hygienist and one trained technician. Both will complete a practice day before the program begins, mounting samplers on volunteers, recording flows and filling in forms, and the hygienist will review the technician's forms for the first week. Each sampled worker will be checked at least twice during the shift to confirm that the sampler is upright, near the collar and running. A sampler found off, inverted or covered by clothing will be recorded on the form, and the sample voided if the problem lasted more than about half an hour.

Data Entry and Review

Results will be entered into a spreadsheet from the laboratory report by one person and checked against the report by a second. Each entry will carry the sample code, group, worker code, date, volume, mass, concentration, flags and any field notes. The hygienist will review every flagged sample before the data are analyzed and will record whether it is kept, adjusted or excluded, and why.

What This Plan Cannot Control

Some variation is real and should not be removed: day-to-day differences in production, wood moisture and machine condition. The plan's job is to keep measurement error small compared with that real variation, so that the variance components estimated later describe exposure, not handling.

References

Harper, M., Akbar, M. Z., & Andrew, M. E. (2004). Comparison of wood-dust aerosol size-distributions collected by air samplers. Journal of Environmental Monitoring, 6(1), 18-22. https://doi.org/10.1039/b312883k

Kenny, L. C., Aitken, R., Chalmers, C., Fabriès, J. F., Gonzalez-Fernandez, E., Kromhout, H., Lidén, G., Mark, D., Riediger, G., & Prodi, V. (1997). A collaborative European study of personal inhalable aerosol sampler performance. Annals of Occupational Hygiene, 41(2), 135-153. https://doi.org/10.1016/S0003-4878(96)00034-8

National Institute for Occupational Safety and Health. (1977). Occupational exposure sampling strategy manual (DHEW [NIOSH] Publication No. 77-173). https://doi.org/10.26616/NIOSHPUB77173