需要进行进一步的毒理学研究来确定影响与起因。
Further toxicological work has to be done to establish cause and effect.
确实，流行病学不能鉴别出影响的起因—它们只能指出令人怀疑的病因与健康问题之间有相关性。
It is true that epidemiological studies cannot identify cause and effect - they can only point to associations between a suspected causative factor and a health problem.
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