This is an excellent question. To date, the six fibers designated to be "asbestos" have been considered highly persistent. However, some recent work by the late Michael Davis of EPA was showing variability in persistence. In fact, Michael was working on a toxic equivalency method, analogous to the one used for dioxins, to be applied to asbestos fibers. In other words, you find the most toxic and persistent type and normalize the total asbestos concentration to that fiber (just as dioxins are normalized to tetrachlorodibenzo-para-dioxin). This means that if asbestos fibers vary in endogenous persistence within the body, they should also vary in environmental compartments, e.g. the reduced and hypoxic conditions in the benthic regions versus upper parts of the water column, after taken up by organisms, etc.

Thanks Daniel for the feedback. Do you may share any reference to the work from  Michael Davis about asbestos? Or from other?

By the way what about the legislation or regulation from EPA about asbestos in aquatic/marine environment. ?

The biopersistence arguments within an organism are illustrated by Bernstein et al (http://www.ncbi.nlm.nih.gov/pubmed/14648356). I believe Davis was trying to normalize this with a type of TEQ. Unfortunately, he died late last year while still working on this.

You are identifying a potentially important knowledge gap, i.e. eco-toxicity of asbestos. The largest concern is inhalation risks to humans, but ingestion is also an important pathway of concern. Regarding water, this is addressed a bit by ATSDR in Chapter 6 of their tox profile for asbestos (http://www.atsdr.cdc.gov/toxprofiles/tp61-c6.pdf). So, water is a pathway and drinking water is an exposure route for human risk. However, you seem to be interested in asbestos as an agent in ecological risk. The U.S. and its states have water quality criteria (number of fibers per volume) for asbestos, but mainly to protect human health. Obviously, if asbestos causes problems in humans, it will also be expected to elicit similar effects in other mammals and other vertibrates, as well as in lower life forms (See UN's http://www.inchem.org/documents/ehc/ehc/ehc203.htm).

Many thanks Daniel for your input, well appreciated!

The fate of asbestos into aquatic/marine environment is still to be investigated mainly if we consider to use marine ecosystem as potential disposal for asbestos wastes (I said potential after encapsulation for instance)

That is a potentially risky proposition, in my opinion. Your question originally seemed to address the persistence of asbestos; however, if the encapsulated asbestos were placed in an aquatic environment, you would also need to know the persistence (half-life) of the encapsulating substance under worst case scenarios (e.g. redox, microbial degradation, hydrolysis, co-solvation, etc.). If the encapsulating substance degrades, the asbestos fibers become bioavailable and can enter the food chain and water supplies.

This is actually the point. I need to convince decision makers with such risks but that should be knowledge/evidence based and I didn't want (have time) to develop the whole experimental designs and settings for such "not" proof of concept.

Of the asbestos fiber types, chrysotile is pH sensitive and degrades in aqueous environment with acidity less than 10.8. As the surface of the mineral is chemically degraded its activity is lost. The literature is replete with references. The amphiboles are a different matter. The USEPA engaged in numerous studies following the contamination of Lake Superior at Silver Bay MN with amphibole gangue minerals (circa 1973). Some of the amphiboles were indistiguishable from amosite (grunerite asbestos) on a analytical TEM level. The EPA studies were extensive (many volumes, 1973 and earlier) and included effects on marine organisms.

Professor A. M. Langer - EES Program - CUNY

The biological persistence of amphiboles as compared to Chrysotile, is an important concept, in human asbestos scenarios, not yet fully grasped by regulatory bodies such as the US EPA. ATSDR or opinionated organizations such as the UN etc.

In addition the behavioral aspects in the environment between the two classes of fibers, are even further from the grasp of such agencies. Sadly to the damage of humans all over the world. In water for example, the amphibole fibers sink to the bottom an average of approximately 100 times faster than Chrysotile. This is also seen in air, only faster. Making Environmental Ambient Air risk assessments for communities or populations, a joke!

More specifically for this thread, I would not expect the actual toxicity of mineral fibers to be an important factor in any benthic community. Since most animals found there are filter feeders/breathers, you will simply suffocate/starve them with asbestos long before any toxic effect will arise. All benthic communities have dealt with asbestos fibers in their environment since life first arose on the planet. Dumping large quantities into the water, as has been done in the Chicago area, is a worry. But long after the benthic community dies from such asbestos dumps, the people living nearby are placed in great danger of many diseases, as the material washes up onto the beaches. Amphibole being of course the greatest, by far, concern.