Application of diluted chlorine dioxide to radish and lettuce nurseries insignificantly reduced plant development

The possible toxicity of a commercial chlorine dioxide preparation (Halox E-100) was evaluated on radish and lettuce seedlings growing in pots under controlled conditions. A single application of various dilutions to radish seedlings growing in a sterile or nonsterile commercial plant substrate only slightly decreased plant dry weight. At the end of the experiments, the plants appeared unaffected by the treatments. Other common plant parameters (root and stem length, number of true leaves) were unaffected or even enhanced. Halox did not reduce the total level of soil bacteria even after four consecutive applications at any dilution rate. In nonsterile soil, high Halox dilution (1:1000) significantly decreased plant dry weight, and the other concentrations (1:10,000; 1:50,000, and 1:100,000) had no apparent effect on the size of the plants. In sterile soil, high concentrations of Halox (1:1000 and 1:10,000) significantly decreased plant growth, but higher dilutions produced no significant reduction in plant dry weight. For radish plants growing in organic matter-free sand only, dilution of 1:10,000 reduced plant growth. On lettuce plants, dilutions from 1:5000 to 1:25,000 did not reduce plant growth. High levels of Halox (1:1000) were toxic to both radish and lettuce seedlings growing in sand and resulted in chlorosis and significant depression of plant growth. Further dilutions of Halox (equivalent to the level used in water disinfection) significantly decreased toxicity for both plant species. Low concentrations of Halox (> 1:50,000) had no apparent effect on the appearance of both plant species. In conclusion, this study suggests that chlorine dioxide-treated drinking water can be considered safe for growing plants; this treatment should be further evaluated using other plant species under more realistic growth conditions.