ADBAC is highly toxic to fish (LC50 = 280 μg ai/L), very highly toxic to aquatic invertebrates (LC50 = 5.9 μg ai/L), moderately toxic to birds (LD50 = 136 mg/kg-bw), and slightly toxic to mammals (LD50 = 430 mg/kg-bw).[4] Benzalkonium chloride solutions of 10% or more are toxic to humans, causing irritation to the skin and mucosa, and death if taken internally.[5]
Benzalkonium chloride is an allergen[6][7][8][9][10][11][12] and several studies have cast doubt on its reputation for safety.[13][14] Some products have been reformulated in light of this research, but it is still widely used in eyewashes, nasal sprays, hand and face washes, mouthwashes, spermicidal creams, and in various other cleaners, sanitizers, and disinfectants. Manufacturers of over-the-counter artificial tears and eye washes became concerned about chemical sensitivity from long-term daily use and have in some products substituted EDTA as a preservative. Some have packaged eye drops in single-use vials with no preservative[15] for sensitive eyes. There has also been concern that long-term use of benzalkonium as a preservative in nasal sprays may cause swelling of mucosa and lead to rhinitis medicamentosa.
Contact lens solutions typically contain 0.002% to 0.01% benzalkonium chloride.[16] K. C. Swan[17] found that repeated use of benzalkonium chloride at concentrations of 1:5000 (0.02%) or stronger can denature corneal protein and cause irreversible damage to the eye. Swan also found that 0.04% to 0.05% solutions of benzalkonium chloride can cause punctures of the corneal epithelium. The disadvantages of using benzalkonium chloride solutions with contact lenses are also discussed in the literature.[18] [19]
A disinfectant containing benzalkonium chloride and the related compound didecyldimethylammonium chloride (DDAC) has been identified as the most probable cause of birth defects and fertility problems in caged mice.[20]
A 2009 study has found that benzalkonium chloride, when used in less than lethal concentrations, resulted in an increased resistance to the disinfectant solution, and a 256-fold increase in resistance of the bacteria Pseudomonas aeruginosa to the ciprofloxacin antibiotic, even though the bacterial colonies had not been previously exposed to the antibiotic.[21]
. But if I am not mistaken, people are probably more inclined to use the method you speak of in a more, uh, lucrative fashion than breaking down benzalkonium chloride, lol.