Effects of a Diphenyl Ether Herbicide (CNP Emulsion) on Mouse Fetuses

We investigated the effects of a diphenyl ether herbicide, a chlornitrophen (CNP) emulsion, on mouse fetuses.

An MO emulsion was used as the experimental chemical twenty percent of this herbicide consisting of CNP. CNP and other components were extracted and evaporated (undegraded solution). The chemical was diluted 10 times by deionized water and then exposed to sunlight until the CNP concentration in the mixture became 10% of the initial CNP concentration. CNP, degradation products, and other materials were extracted from the mixture and evaporated (degraded solution).

The undegraded and degraded solutions were administered subcutaneously to the backs of pregnant mice from the 6th to 15th fetal day, once daily. The mice were sacrificed on the 18th day of pregnancy. The number of fetuses and implantations, their weights, externals and skeletons were observed. Infant mice born from maternal mice treated in the same way as above were weighed once a week.

Mean fetal body weights of the undegraded and degraded solution dose groups were significantly lower than those of the control (p < 0.001). Fetal skeletal abnormalities were also higher than those of the control. The degraded solution dose group differed particularly in this regard from the control (p < 0.05). In the degraded solution dose group, all 21 newborn infants from two maternal mice out of a total of 43 newborn infants from four maternal mice died within one week.

The above results suggest that the degraded solution of CNP is no less noxious on mouse fetuses than the undegraded solution. Thus, more consideration should be given not only to the original chemicals but to the degradation products as well when assessing agricultural control chemicals for their safety.