Recently mainland China, which primarily burns coal for energy, also undertook a survey of birth defects. They discovered that because the pollution from coal-burning is relatively higher in the summer, the rate of children with birth defects is higher than that in the winter.
仍以燒煤為主的中國大陸，最近也對畸型兒做調查，發現夏季因為燒煤產生的污染性較高，畸型兒發生率就高過冬天。