Germinomas and teratoid siphon anomalies in softshell clams, Mya arenaria, environmentally exposed to herbicides

Our plain-English summary of Germinomas and teratoid siphon anomalies in softshell clams, Mya arenaria, environmentally exposed to herbicides, by G.R. Gardner, P.P. Yevich, J. Hurst, et al (Environmental Health Perspectives, 1991).

The study

• Authors: G.R. Gardner, P.P. Yevich, J. Hurst, P. Thayer, S. Benyi, J.C. Harshbarger, R.J. Pruell
• Journal: Environmental Health Perspectives
• Published: 1991;90:43-51
• Cited by: 35 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Seminomas and dysgerminomas are epizootic in softshell clams, Mya arenaria, from three Maine estuaries contaminated with herbicides. The first epizootic was discovered in 22% of clams collected as Searsport near Long Cove Brook and three culverts that conveyed heating oil and jet fuel spilled from a tank farm in 1971. Data from subsequent epizootiological studies and a series of long-term experimental exposures of softshell clams to no. 2 fuel oil, JP-4, and JP-5 jet fuel at the U.S. EPA, Environmental Research Laboratory in Narragansett, Rhode Island, and in the field did not support an etiology by these petroleum products. In the two recent epizootics reported here, the germinomas have been observed in 3% of the softshell clams collected from Roque Bluffs near Machiasport and from 35% of softshell clams collected from Dennysville. Mya collected at Dennysville had pericardial mesotheliomas and teratoid siphon anomalies in addition to gonadal neoplasms. Estuaries at Dennysville had been contaminated by herbicides in a 1979 accidental spray overdrift during aerial application of Tordon 101 to adjacent forests. Further investigation determined widespread use of the herbicides Tordon 101, 2,4-D,2,4,5-T, and other agrochemicals in an extensive forestry and blueberry industry in both the Roque Bluffs and the Dennysville areas. Herbicide applications at Searsport were confirmed for railroad property bordering Long Cove estuary and for Long Cove Brook adjacent to the estuary where a highway department reportedly cleans its spray equipment. Herbicide contamination is the only common denominator identified at all three sites where Mya have been found with gonadal neoplasms.(ABSTRACT TRUNCATED AT 250 WORDS)

In plain English

This article does not concern asbestos. It is a field study of softshell clams (Mya arenaria) in eastern coastal Maine and their possible exposure to herbicides. The authors examined clams from several clam flats under the microscope. They also summarized their earlier laboratory work, in which clams exposed to no. 2 fuel oil and JP-4 and JP-5 jet fuels showed no link to gonadal tumors. Gonadal tumors (germinomas) were found in 2 (3%) of 58 clams from Great Cove at Roque Bluffs. Near Dennysville, an area accidentally sprayed with the herbicide Tordon 101 in 1979, they were found in 28 and 36% of clams from two Hobart Stream sites and in 32 to 40% of clams from Hardscrabble River. None were seen in reference clams from Hallowell Island. Extra siphons occurred in 7% of Hardscrabble River clams. Two of four clams supplied by a local resident had mesotheliomas of the heart lining, and the authors stated that the cause of these was not apparent. Herbicides were not measured in the clams. The authors concluded that herbicide contamination was the only common factor found at the three tumor sites, and they called for further study.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Field survey of clam populations with tissue examination under the microscope (histopathology) and chemical analysis of pooled clam samples, together with a summary of the authors' earlier laboratory exposure studies
• Who was studied: Softshell clams (Mya arenaria) from estuaries in eastern coastal Maine. Groups were: 58 clams from Great Cove at Roque Bluffs (October 1981); 425 clams from five sampling stations at Dennysville, including the Hallowell Island reference station (Hardscrabble River collections in March 1980); more than 100 adult clams from four other locations (Indian River, Snare Creek, Masons Bay, Woodruff Cove)
• Exposure: Herbicides, not asbestos. The authors studied Tordon 101 (picloram and 2,4-D), accidentally sprayed on Dennysville in 1979, and 2,4-D, 2,4,5-T and other agrochemicals used in forestry and blueberry farming. Earlier laboratory work examined no. 2 fuel oil and JP-4 and JP-5 jet fuels
• Main results:
  • Gonadal tumors were found in 2 (3%) of 58 clams from Great Cove at Roque Bluffs
  • In follow-up sampling near Dennysville, germinoma prevalence was 28 and 36% at two Hobart Stream sites and 32, 32 and 40% at three Hardscrabble River locations
  • No germinomas were seen in clams from the Hallowell Island reference station
  • Supernumerary (extra) siphons were seen in 7% of Hardscrabble River clams and in none from Hobart Stream. All clams with the siphon disorder also had gonadal tumors
  • Multiple mesotheliomas of the heart's outer lining (epicardium) were found in two of four clams collected from Hardscrabble River by a Dennysville resident
  • Chemical contaminant levels in clam samples from all three locations were very low. A higher PCB concentration (120 ng/g dry weight) was found at the reference site, and benz(a)pyrene ranged from 3.06 to 4.29 ng/g between stations
  • In the authors' laboratory studies, no relationship between gonadal tumors and petroleum hydrocarbons was evident in clams exposed for 45 to 360 days
• The authors' conclusion: The authors concluded that herbicide contamination was the only common factor they identified at all three sites with tumorous clams. They also concluded that laboratory studies and closer examination of herbicide use near shellfish resources were warranted
• Limitations the authors state:
  • Herbicide levels in the clams were not measured
  • Sediment chemical analyses were not performed at all three sites
  • Records of herbicide volumes sprayed before 1979 were not available
  • The authors could not show a link between herbicides and the siphon anomalies, and they said these could be inherited
  • The cause of the clam mesotheliomas was not apparent

Topics

Medical terms in this study, explained in our Lexicon: Etiology, Pericardial Mesothelioma, Neoplasm.

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