the discharge of toxic waste gas and dust into the atmosphere shall be strictly restricted when such discharge is really necessary the discharged gas or dust must undergo purification treatment
确有必要向大气排放有毒废气、粉尘的，应当严格限制;排放的废气、粉尘必须经过净化处理
以上为机器翻译结果，长、整句建议使用 人工翻译 。