Memory deficits and industrial toxicant exposure: a comparative study of hard metal, solvent and asbestos workers

Our plain-English summary of Memory deficits and industrial toxicant exposure: a comparative study of hard metal, solvent and asbestos workers, by C.M. Jordan, R.D. Whitman, M. Harbut (The International Journal of Neuroscience, 1997).

The study

• Authors: C.M. Jordan, R.D. Whitman, M. Harbut
• Journal: The International Journal of Neuroscience
• Published: 1997;90(1-2):113-28
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Memory functioning was examined in ex-factory workers with hard metal disease, resulting from exposure to alloys utilizing cobalt. Since these workers are also exposed to organic solvents and may suffer from chronic hypoxia as a result of their pulmonary disorder, solvent and asbestos workers, as well as an unexposed matched sample, served as controls. Results demonstrated deficits in the allocation of attentional resources and in short-term verbal memory. A pattern of findings across several tests suggested that repetition or delay is important for adequate memory performance in individuals exposed to hard metal, implicating a deficit in encoding or slowed consolidation.

In plain English

This study compared memory and attention test results in four groups recruited through a midwestern occupational medicine clinic and through advertisements. The groups were 16 former hard metal grinders treated for lung disease attributed to tungsten carbide and cobalt exposure, 13 solvent-exposed workers with lung disorders, 15 ironworkers, millwrights and asbestos workers treated for asbestosis, and 21 unexposed healthy controls. The asbestosis group was included to account for the possible effects of lung disease on memory. The asbestos group's exposure was estimated at about 7 to 35 years, and the article did not name a fiber type. Significant differences generally appeared only between the hard metal workers and the healthy controls, who did better on short-term verbal memory and attention tasks. On one cued faces test, the asbestos workers scored better than the hard metal workers. The authors concluded that the hard metal workers had difficulty encoding new memories. They found mixed support for effects beyond solvent exposure and low oxygen, and noted that larger samples might have shown differences between the asbestos and hard metal groups.

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: Comparative study of memory and attention test performance in four groups: hard metal workers, with solvent workers, asbestos workers with asbestosis and unexposed people as comparison groups
• Who was studied: 16 former hard metal grinders, 13 solvent-exposed workers with lung disorders, 15 ironworkers, millwrights and asbestos workers being treated for asbestosis, and 21 unexposed healthy controls. The workers came from a midwestern occupational medicine clinic and the controls from advertisements. One asbestos worker (significant head injury) and one control (severe long-term alcohol abuse) were excluded from analysis. Dates of the study are not given.
• Exposure: Asbestos group: exposed to asbestos for an estimated 7 to 35 years (mean 20.8). Most had been removed from exposure 1 to 13 years before testing, and two still worked where exposure was possible. No fiber type is named. Hard metal group: tungsten carbide and cobalt dust and mist with mixed organic solvents, for 2 to 35 years. Solvent group: various solvents for 5 to 30 years.
• Main results:
  • On the Word Triad attention task, the hard metal group's average drop in recall between 0 and 9 seconds (6.00) was significantly greater than that of the normal control group (2.75).
  • On the Wechsler Memory Scale-Revised, the normal control group's Verbal Memory Index scores exceeded those of the hard metal group and the solvent group.
  • The hard metal and solvent groups showed almost an 11-point gap between their Verbal and Visual Memory Index scores. The asbestos workers and normal controls showed no notable gap of this kind.
  • On the Benton Visual Retention Test of short-term visual memory, group differences were not significant.
  • On the California Verbal Learning Test, cueing did not improve recall more in one group than another, so no group showed a retrieval deficit.
  • On the first learning trial of the California Verbal Learning Test, hard metal workers recalled significantly fewer words than normal controls. Contrasts between the other groups (including the asbestos workers) and the hard metal workers were not significant. By trial 5, no group differences were found.
  • On the cued Faces Test of remote memory, the asbestos workers (mean 70.73) performed better across decades than the hard metal workers (mean 52.47). The group-by-decade interaction was not significant.
  • Overall, significant group differences generally appeared only between the normal control and hard metal groups.
  • On many Word Triad Test scores, the authors described a modest, progressive decline in performance from normal controls to the asbestosis group to the solvent group to the hard metal group.
• The authors' conclusion: The authors concluded that hard metal workers have difficulty in the encoding phase of memory, perhaps because of impaired attention or difficulty allocating attention. They found only mixed support for the idea that hard metal disease affects memory independently of solvent exposure and low-level hypoxia.
• Limitations the authors state:
  • Small samples. The authors stated that larger samples might have detected significant differences, at least between the asbestos and hard metal groups.
  • The solvent group was made up of nearly all solvent patients seen at the clinic, so it could not be matched demographically to the hard metal workers in advance.
  • The amount of asbestos exposure was difficult to estimate.
  • Only five current carbon monoxide diffusing capacity values were available for the hard metal workers.
  • Only memory and attention were studied. Whether these workers have other cognitive difficulties is unknown.

Topics

Medical terms in this study, explained in our Lexicon: Hypoxia, Consolidation.

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