Thursday, July 28, 2016

Orchard Arsenic and Lead Legacy

Spraying dry lead on apple trees
(Washington State Historical Society, A.G. Simmer, 1925)

An effective means of controlling pests in orchards was to spray the trees with a mix of lead and/or arsenic. This practice continued into the 1950s. As lead and arsenic are elements, they do not go away. As such old orchards are often locations of residual contamination. Other pesticides may be present as well from past agricultural activities, but the long term use of lead and arsenic simply do not go away.

Conversion of agricultural land to residential or other uses has created a potential risk to human health due to the residual soil contamination. Washington State Department of Ecology has been attempting to address this issue and has conducted numerous soil cleanups where schools have been located on former orchards with elevated lead and arsenic levels in the soil (Former Orchard Lands). Thus far 26 school sites have undergone cleanups. The cleanups often simply cover the soils so there is no direct contact with the arsenic and lead. This is an effective approach but does require periodic inspection and an awareness by the property owners (school districts).

While the school sites have been treated, neighborhoods within former orchard areas face the same problem. An educational program has been the approach used by Ecology and local health departments. Some newer residential areas have gone through cleanups since the hazard has been recognized, but it is a significant planning issue for local governments in cities and counties where urban growth has been expanding into former commercial orchards in eastern Washington.          


Dave said...

"As lead and arsenic are elements, they do not go away."

Love the blog; I have it bookmarked and I check back often for updates. I feel the need to call you out on this bit of silliness, however. Now, I don't know anything specific about the persistence of these metals in the environment. But I can tell you with certainty that any such persistence is not due to their being elements. Furthermore, I can tell you with even more certainty that elemental lead and/or arsenic was NOT what was being sprayed.

Dan McShane said...

Dave: I did not mean to imply that pure lead or arsenic was sprayed. I left off the molecular make up of the formulations that contained the lead and arsenic as well as any molecular bounding that takes place in the soil. By persistence I mean that the arsenic and lead will not break down (the are elements). Other pesticides will over time break down. If you have other concepts about persistency that you can tell, please do.