The adsorption of polyaromatic hydrocarbons on natural and chemically modified asbestos fibers

Our plain-English summary of The adsorption of polyaromatic hydrocarbons on natural and chemically modified asbestos fibers, by H. Menard, L. Noel, J. Khorami, et al (Environmental Research, 1986).

The study

• Authors: H. Menard, L. Noel, J. Khorami, J.L. Jouve, J. Dunnigan
• Journal: Environmental Research
• Published: 1986;40(1):84-91
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Many reports indicate that the carcinogenic (genotoxic) potential of benzo[a]pyrene (B[a]P) may be enhanced several-fold by the promoter (epigenetic) effect of asbestos particles. This promoting effect could be related to the fact that when B[a]P is adsorbed onto the particles, there is a resulting enhanced transport and uptake of the carcinogen into microsomial membranes. These in vitro data bear relevance to the epidemiological studies which indicate an association between exposure to inhaled asbestos dusts and the high incidence of pulmonary cancers in smokers. Using HPLC, it has been observed that B[a]P has great affinity for natural asbestos fibers, and that chemical modification of natural chrysotile with POCl3 results in the complete loss of this adsorption potential of chrysotile for benzo[a]pyrene.

In plain English

This was a laboratory chemistry study, not a study of people, cells or animals. The authors tested two commercial grades of Quebec chrysotile asbestos, QS 4T (asbestos-cement) and the shorter QS 7D (felt), both natural and after treatment with phosphorus oxychloride (POCl3), which deposits phosphate on the fibers. Using high-pressure liquid chromatography, they measured how strongly benzo[a]pyrene and other polyaromatic hydrocarbons stuck to the fibers. Treated fibers had less surface area (5 and 4 square meters per gram for treated 7D and 4T, versus 10 and 13 untreated) and a negative instead of positive surface charge. Benzo[a]pyrene had a net retention time of 28.0 minutes on natural 7D fibers but 0.08 minutes on treated 7D fibers. On natural 4T fibers it was 25 minutes, but a larger amount was injected there (1000 nmole) than on treated 4T fibers (20 nmole), which showed no adsorption. The authors concluded that treated fibers nearly completely lost the ability to adsorb and carry some known initiators of lung cancer present in tobacco smoke. They said this should be confirmed by biological tests.

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: Laboratory (in vitro) chemistry study comparing natural and chemically treated chrysotile fibers using infrared spectroscopy, thermal analysis, surface area and surface charge measurements, and adsorption measured by high-pressure liquid chromatography
• Who was studied: Four chrysotile asbestos samples: two Quebec Standard commercial grades, QS 4T (asbestos-cement grade) and QS 7D (shorter, felt grade), each tested untreated and treated with POCl3
• Exposure: Chrysotile asbestos fibers, natural and phosphated (treated with phosphorus oxychloride, POCl3), exposed to benzo[a]pyrene and other polyaromatic hydrocarbons (fluoranthene, pyrene, phenanthrene, anthracene, fluorene, naphthalene) in toluene
• Main results:
  • Treated fibers contained 1.8% phosphate by weight (QS 7D) and 0.8% (QS 4T)
  • Specific surface area was 10 and 13 square meters per gram for untreated QS 7D and 4T, and 5 and 4 square meters per gram for the treated samples
  • Zeta potential (surface charge) was +20 and +18 mV for untreated QS 7D and 4T, and -39 and -36 mV for the treated samples
  • Benzo[a]pyrene net retention time on QS 7D fibers was 28.0 minutes for natural fibers and 0.08 minutes for phosphated fibers
  • Benzo[a]pyrene net retention time on QS 4T fibers was 25 minutes for natural fibers and phosphated 4T fibers showed no adsorption. Table 2 lists the natural-fiber benzo[a]pyrene injection as 1000 nmole, against a 20 nmole column heading for the treated fibers, so the two amounts were not the same.
  • The pressure needed to push solvent through the column was 10 times lower with phosphated fibers than with natural fibers
  • The authors interpreted the thermal analysis as showing that POCl3 first reacts with alkaline impurities associated with the chrysotile, forming hydrated magnesium phosphate
• The authors' conclusion: The authors concluded that phosphate treatment caused a nearly complete loss of the fibers' ability to adsorb and carry some known initiators of lung carcinogenesis present in tobacco smoke. They related this to a strategy to design safer fibers and said it should be confirmed by biological assays.
• Limitations the authors state:
  • The authors state the finding needs confirmation by cocarcinogenicity and comutagenicity biological assays. No biological testing was done in this study.

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic, Chrysotile.

Related studies

• Mass transfer rates of polycyclic aromatic hydrocarbons between micron-size particles and their environment--theoretical estimates — P. Gerde, P. Scholander (1989)
• Effects of particulate matter on rates of membrane uptake of polynuclear aromatic hydrocarbons — D.R. Bevan, S.C. Riemer, et al. (1981)
• Elemental modifications and polycyclic aromatic hydrocarbon metabolism in human fibroblasts — R.W. Hart, F.B. Daniel, et al. (1980)
• Sorption of nonpolar aromatic contaminants by chlorosilane surface modified natural minerals — P. Huttenloch, K.E. Roehl, et al. (2001)
• Transport of a carcinogen, benzo[a]pyrene, from particulates to lipid bilayers: a model for the fate of particle-adsorbed polynuclear aromatic hydrocarbons which are retained in the lungs — J.R. Lakowicz, D.R. Bevan, et al. (1980)
• Aryl hydrocarbon hydroxylase induction in mitogen-stimulated lymphocytes by benzanthracene or cigarette tars adsorbed to asbestos fibers — T.L. McLemore, W.T. Jenkins, et al. (1979)

Browse more research in Environmental Research, or return to medical research.