Science of Conservation: Pesticides in Museum Collections

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CCI Newsletter, No. 33, May 2004

Science of Conservation: Pesticides in Museum Collections

by Jennifer Poulin, Conservation Scientist, Analytical Research Laboratory

Since 1987, CCI's Analytical Research Laboratory has analysed over 1100 natural history specimens and 600 artifacts in Canadian Aboriginal collections. The goal was to detect the presence of lead-, arsenic- and mercury-containing pesticides, such as arsenical soaps, lead arsenate and mercuric chloride. A portable X-ray fluorescence spectrometer (XRF) was used for the analysis.

The pesticides used to treat and protect collections from infestation and deterioration were not, however, limited to inorganic pesticides. There are hundreds of organic pesticides that one might encounter while working with museum objects. In the past, it was normal to treat artifacts with organic and inorganic pesticides. Often the type and amount of pesticides and preservatives applied to objects varied from collection to collection. However, treatment records may be incomplete or may not even exist at all. Detecting and identifying these compounds is crucial to assess health risks and to develop protocols for handling and storing the objects to minimize health risks.

The Analytical Research Laboratory is currently developing methods to detect organic pesticides using gas chromatography mass spectrometry (GC-MS) to supplement the inorganic screening methods and, therefore, to provide a complete survey of a collection. During a recent visit to the McCord Museum in Montreal, the pilot program of this new service was launched. Documentation suggested that some of the objects in its Aboriginal collection may have been treated with DDT before the museum acquired them. Approximately 100 Canadian Aboriginal artifacts were surveyed. The artifacts were all in very good condition and appeared to be well-preserved — one sign that pesticides may have been applied at some point. The on-site analysis XRF indicated that most of the collection was not contaminated by inorganic pesticides. Samples to be analysed by GC-MS were collected using three different, non-destructive techniques:

• The air in the storeroom was sampled with passive diffusion air cartridges.
• Artifacts were individually sampled using cotton swabs, lightly drawn across surfaces and into crevices where unseen residues may have collected.
• A gentle micro-vacuum filter system was used to draw air and lightweight particles from the surface of the artifacts onto glass fibre filters.

The analysis indicated that some, but not all, of the artifacts were treated with or contaminated by organic pesticides such as DDT, DDD, methoxychlor and perthane. In some cases, only trace amounts of these compounds were detected, yet other artifacts were found to have much higher levels. Analysis of the air monitors did not indicate the presence of pesticides in the air, perhaps because most of the pesticides found on the artifacts have very low vapour pressures.

One very encouraging outcome of the survey was the success of the handmade cotton swab as a sampling tool. The swabs were used to gently gather residue, then sealed in containers for future examination. This may prove to be an inexpensive and useful preliminary screening method for collections where it is suspected that organic pesticides have been applied.

These surveys help assess the health risk for those who will have contact with the artifacts, such as museum staff or Aboriginal communities to which artifacts are repatriated.

CCI is currently involved in national and international conferences, seminars and working groups concerning the contamination of museum collections by pesticide residues.