The Bronowski Institute

Early in 1991, shortly after setting up the Bronowski Institute we were examining various hypotheses regarding the possible causative factors in depression. With a past interest in the toxicity of heavy metals in biological systems (fluoride and aluminium) we were curious as to whether ubiquitous forms of heavy metals and metalloids might be neurotoxic and thereby causing depression with chronic exposure. With CCA (copper, chromium and arsenic) treated timber being a timber preservation that had been used extensively in the building industry for the past century we entertained the possibility that the active metals in this timber might be important in the aetiology of depression. With our laboratory geared up to test the feasibility of this hypothesis we undertook several pilot and formal studies to determine if this might be the case. In the first instance, we examined the health and performance of rodents that were exposed for more than 40 generations and were nested on the material from birth and through their adulthood. Not only was there a total absence of any genetic abnormalities, but the litters were significantly bigger than those housed on standard bedding material with a total absence of any respiratory distress that is indigenous in these colonies. Furthermore, when we tested CCA treated bedding material against other forms of timber bedding such as hardwood, untreated radiata pine and cypress, animals raised in CCA were healthier and thrived better than in any of the other forms of timber bedding. In fact, it is interesting to note that the “CCA scares” (so it seems that they are not based in fact) that emerge from time to time over the past 20 years have raised public awareness about the potential dangers of CCA and consequently cypress is the substitute that is now marketed in its place. This was viewed as a particularly potent issue in regard to playgrounds that were constructed from CCA. What the public doesn’t know is when neonatal rats are raised on these various native timbers the mortality rate with cypress was well over 90%, far greater than it was for CCA (which, by the way, was zero). From this we surmised that the tannins and endogenous oils in the cypress and other native timbers are more toxic than are the elements in the CCA. In addition, the fact that the treated timber had to be dried prior to treatment meant that the endogenous oils were removed prior to processing.

In additional studies where we examined the proliferation of earthworms raised in CCA treated timber mulch and various plants grown in CCA fortified soil and even the plasma levels of copper, chromium and arsenic in the blood of people that had ingested vegetables raised therein all pointed to the same conclusion. That is, that it is compatible with any living organism that comes in contact with it. In fact, when given the choice, earthworms not only thrive in it but they migrate into it, compared to all other mulches tested. As a final feather in the cap of CCA treated timber, when we examined CCA treated structures that were used for construction and gardening purposes in rainforest areas we found that algae, lichen, mosses and delicate ferns flourished when it grew adjacent to or directly on CCA treated structures. Reports that followed presented some of the data depicting our ongoing projects in an attempt to assess the environmental and biological impact of various timber preservatives. Our neurotoxicological work on this theme will continue not only to help industry in identifying safety features of timber preservatives, but to examine the biological and environmental compatibility of these substances for human use and for applicability in the broader ecology.

Environmental Toxicology