Yen Law Yen, Jayaprakash P T
Forensic Division, Department of Chemistry, Malaysia, Jalan Sultan, 46661 Petaling Jaya, Selangor Darul Ehsan, Malaysia.
Forensic Sci Int. 2007 Jul 20;170(1):1-7. doi: 10.1016/j.forsciint.2006.08.020. Epub 2006 Oct 4.
Detection of diatom frustules in bone marrow (diatom test) is used for diagnosing ante-mortem drowning where the usual signs of drowning are not present in dead bodies recovered from water. However, controversies over the reliability of diatom test results are continuing. There have been indications on the possibilities of diatoms entering into systemic circulation from atmospheric air, food and drink. While diatoms have been demonstrated in the gut content of edible marine forms such as shrimps and clams, the present study, for the first time, provides empirical evidence on the prevalence as well as abundance of diatom frustules in the samples of cooked non-vegetarian foodstuffs that impend human consumption in Kelantan, Malaysia. It is found that 50 g each of cleaned and cooked prawns and of clams impending human consumption contain about 8360 and 29,054 diatom frustules, respectively. A person accustomed to prawn and clam food would be ingesting an estimated 2 million diatoms in a single year. Considering the suggestion that detection of five diatom frustules in 10 g of bone marrow would suffice for concluding drowning as mode of death, and the fact that there is yet no proof that diatom frustules do not enter into the human systemic circulation through the digestive tract, the estimated number of diatom frustules routinely ingested acquires significance since entry of a few of such ingested frustules into the systemic circulation can lead to false positive test results. The findings of this research raise two important issues: first, population based routine food related diatom ingestion requires to be estimated, and, second, studies have to be initiated to categorically prove or disprove the possibility of entry of diatom frustules into the systemic circulation via the digestive tract.
在骨髓中检测硅藻壳（硅藻检测）用于诊断生前溺水，对于从水中打捞的尸体，若不存在溺水的常见迹象时可采用此方法。然而，关于硅藻检测结果可靠性的争议仍在持续。有迹象表明，硅藻有可能通过大气、食物和饮料进入体循环。虽然在虾和蛤蜊等可食用海洋生物的肠道内容物中已发现硅藻，但本研究首次提供了实证证据，证明在马来西亚吉兰丹州即将供人类食用的非素食熟食样本中，硅藻壳的流行程度和丰度情况。研究发现，每份50克即将供人类食用的清洁熟虾和熟蛤蜊分别含有约8360个和29054个硅藻壳。一个习惯食用虾和蛤蜊的人一年估计会摄入200万个硅藻。考虑到有观点认为在10克骨髓中检测到5个硅藻壳就足以判定溺水为死因，且尚无证据表明硅藻壳不会通过消化道进入人体体循环，那么常规摄入的硅藻壳估计数量就具有重要意义，因为少量摄入的硅藻壳进入体循环可能导致假阳性检测结果。本研究结果提出了两个重要问题：第一，需要对基于人群的与食物相关的常规硅藻摄入量进行估计；第二，必须开展研究以明确证明或反驳硅藻壳通过消化道进入体循环的可能性。
