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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Tuesday 27th December 2011 

Day 2 of our look at the American Association of Poison Control Centers (AAPCC) 2010 Annual Report of the National Poison Data System (NPDS). Last Friday, I looked at some of the difficulties in interpreting the data because there is a lot of detailed breakdown on the total numbers and very detailed analysis of the deaths caused by poisoning but it is harder to understand what actual plant types resulted in incidents requiring the intervention of a healthcare facility.

Today, I thought I would try and see if there is a correlation between number of case mentions and the outcomes because, it seems to me, differences might indicate attitudes to the potential risk for harm. I’ve often said that, as far as it is possible to tell, the public perception of the risk from Laburnum in the 1970s meant that children were suspected of being poisoned by it if they were seen close to a tree. I doubt if parents would react the same way to seeing their child close to, say, mother’s make-up bag.

The NPDS report ranks the top 25 categories for human exposure calls and, on that basis, plants were the 17th highest cause of contact with a poison control center (pcc). That’s based on the ‘case mentions’ but the analysis by age and outcomes deals only with ‘single exposures’, that is where only one substance is involved. The AAPCC says this is ‘to improve precision and avoid misinterpretation’. Taking the number of ‘single exposures’ moves plants up to 13th in the overall ranking.

When I looked at the percentage of single exposures that required treatment in a health care facility (%HCF) plants moved from 13th to 19th and, for the percentage of single exposures that produced ‘Major’ outcomes, plants moved to 17th. So, it seems that the total pcc activity related to plants is in excess of the relative seriousness of the cases.

I did start to look at deaths but there were 5 deaths or fewer in 11 of the top 25 categories meaning that one death up or down could make a big difference to the ranking. Plus, as explained above, the category breakdown for deaths only deals with the 764 deaths resulting from ‘single exposures’ rather than the 1,146 total for pcc case mentions or the 1366 individually analysed with the inclusion of 220 fatalities collected from other sources. That’s why I chose major outcomes as the measure of seriousness of poisoning.

So, if ranking plants on total calls overstates their relative seriousness, there must be categories where this measure produces an understatement.

Two that stand out are ‘Stimulants and Street Drugs’, which is only 19th in the overall ranking but 3rd for %HCF, and ‘Anticonvulsants’, which is 20th overall but 4th for %HCF. Just to add to the difficulty of drawing any conclusions, ‘Stimulants and Street Drugs’ is at the top of the ranking for ‘Major’ outcomes as a percentage of single exposures but ‘Anticonvulsants’ falls to 20th.

Table 22A offers an age breakdown for single exposures with four age bands. I looked at the highest, age 20 and over, to see if there was any correlation between the percentage of adult exposures and the %HCF. Just looking at the ranking of adult percentages does seem to show that there are ‘adult’ poisons and ‘child’ poisons. 58% of single exposures for ‘Sedative/Hypnotics/Antipsychotics’ were for adults but, at the other end of the ranking, only 6% of exposures to ‘Arts/Crafts/Office Supplies’ were aged 20 or over. Also, the former ranked 3rd for percentage of ‘Major’ outcomes whereas the latter was 25th on that measure.

There does seem to be some loose correlation because seven of the top ten for percentage of adult exposures are also in the top ten for %HCF and six of them are in the ‘Major’ outcome top ten. The most striking single category is ‘Fumes/Gases/Vapors’ which is 24th in the overall ranking but 8th for both %HCF and ‘Major’ outcome.

It is dangerous to over-interpret this data and think firm conclusions can be drawn. For example, ten of the top twenty five categories resulted in fewer than 100 ‘major’ outcomes and, clearly, there must be some blurring of the line between deciding a case is ‘Moderate’ rather than ‘Major’ so the ranking for ‘Major’ outcome could be changed by just a few cases being wrongly classified.

However, it does seem that some categories result in more calls as a result of fear of poisoning of children and plants, with only 14% of exposures being adults, is one of those categories.

The figures for ‘Plants’ should be for the plants themselves rather than extracted substances and, of course, there are many pharmaceuticals derived from plants. ‘Analgesics’ ranks at No1 for total case mentions and retains that No.1 position when it comes to the percentage of single exposures with a ‘Major’ outcome. It also, in quantity, produced the highest number of deaths, 213 of the 764 analysed in Table 22A. Many of these substances are, originally if not today, plant derived and, in a future entry, I want to see what can be determined about plant-derived poisonings.