Thanks for great question and answers; as far as i know : Boric acid and borates are released into the environment by human activities and ......Please kindly read the reference========

Boric acid is a weak acid with a pKa of 9.2 and exists primarily as the undissociated acid (H3BO3) in aqueous solution at physiological pH, as do the borate salts. Therefore, the toxicity associated with the boron compounds listed in Annex II to this mandate is expected to be similar based on boron equivalents. Boron oxide will produce similar effects because it is an anhydride that reacts exothermically with water in the body to form boric acid. In aqueous solutions of sodium perborate at room temperature an equilibrium between sodium perborate and hydrogen peroxide/sodium metaborate is instantly established. Sodium metaborate is the salt of a strong base (sodium hydroxide) and a weak acid (boric acid). Therefore, it is expected to be present in aqueous solutions at environmental temperature and pH mainly as the weakly dissociated boric acid. Disodium octaborate tetrahydrate is a solid solution of boric acid and disodium tetraborate decahydrate. Disodium octaborate tetrahydrate is converted into boric acid//borate upon dissolution in water

Reference: https://ec.europa.eu/health/sites/health/files/scientific_committees/consumer_safety/docs/sccs_o_027.pdf

As far as I know, boric acid and borax are substances that are potentially dangerous for the environment, especially for soil and water resources.

There is indeed a discussion of whether boron-based preservatives are "environmental-friendly" or not. All the chemicals we use (even natural/organic extractives) and processes will have an impact. To be honest I don't think there is the best and the only one. But certainly, there will be the most appropriate one, depending on the situation and application.

Well, I agree with Goran Schmidt that there are two main aspects to discuss here.

First of all, in terms of boron availability. It is not everywhere and it demands mining operations. However, the use of boron-based chemical for wood/bamboo treatment is very low compared to other industrial activities. On the other hand, in terms of life cycle perspective of treated bamboo, for example, the boron products along with transportation are the main contributors to CO2 emissions.

Any chemical should be handled with care! Even if it is not considered toxic to humans. I think especially for informal bamboo treatment operations, workers should be completely protected with PPE and avoid constant contact with the treatment solution. As Prof. Montoya pointed it out, boron-based treatments are very effective with broad-band protection. If we consider all the commercial preservatives available and correlate them with their treatment performance, I am certain borax/boric acid/DOT will appear as the best options in a balance between cost/effectiveness/hazard, especially for bamboo. Always taking into account, of course, that borax/boric acid are extremely leachable and should only be used in protected environments. Additionally, we need to think about the use of boron compounds during treatment. DOT (disodium octaborate tetrahydrate), for example (which is the one I recommend), has close to neutral pH at concentrations between 5-10%, it is very soluble, and is not corrosive. These characteristics facilitate the treatment process.

Boron is an essential micronutrient for soil (in very low concentration, ppm scale). The disposal is only a problem if it is done unproperly, without guidance and concentrated in small areas. This is very important. Nevertheless, it is possible to recover and reuse treatment solutions by conditioning and cleaning operations. In a process, we should avoid and diminish waste/disposals.

Last but not least, I think this is a very important discussion that should be handled with care, considering all the risks involved. Although there are studies pointing out the toxicity of boric acid for reproduction, if used in the correct way (as any other chemical), I don't see it as a threat especially considering the cost/effectiveness/hazard balance. However, I totally agree that more studies are necessary to address this issue.

Well, just food for thoughts :)

Thanks for great question and answers; as far as i know : Boric acid and borates are released into the environment by human activities and ......Please kindly read the reference========

Boric acid is a weak acid with a pKa of 9.2 and exists primarily as the undissociated acid (H3BO3) in aqueous solution at physiological pH, as do the borate salts. Therefore, the toxicity associated with the boron compounds listed in Annex II to this mandate is expected to be similar based on boron equivalents. Boron oxide will produce similar effects because it is an anhydride that reacts exothermically with water in the body to form boric acid. In aqueous solutions of sodium perborate at room temperature an equilibrium between sodium perborate and hydrogen peroxide/sodium metaborate is instantly established. Sodium metaborate is the salt of a strong base (sodium hydroxide) and a weak acid (boric acid). Therefore, it is expected to be present in aqueous solutions at environmental temperature and pH mainly as the weakly dissociated boric acid. Disodium octaborate tetrahydrate is a solid solution of boric acid and disodium tetraborate decahydrate. Disodium octaborate tetrahydrate is converted into boric acid//borate upon dissolution in water

Reference: https://ec.europa.eu/health/sites/health/files/scientific_committees/consumer_safety/docs/sccs_o_027.pdf

"Environmentally-friendly" is a marketing term tht has no technical meaning. suggest folks consider the US EPA human and environmental health assessment of boric acid/borates https://www3.epa.gov/pesticides/chem_search/reg_actions/reregistration/fs_PC-011001_1-Sep-93.pdf