Many chemical fertilizers are acceptable to use on your lawn as long as children and animals are kept away from it until it has been absorbed. The fertilizer may be blown by the wind, and if consumed in high numbers, it can be hazardous. It should be completely safe to walk or play on once it has been absorbed into the soil naturally or with the aid of irrigation. Just make sure you don't fertilize too much or you'll wind up doing more damage than good!