Metal residues after cremation
BMJ 1994; 308 doi: https://doi.org/10.1136/bmj.308.6925.390 (Published 05 February 1994) Cite this as: BMJ 1994;308:390
- M Barry
- Correspondence to: Mr M Barry, Mayday University Hospital, Thornton Heath, Surrey CR7 7YE.
- Accepted 23 November 1993
Cremation takes place in two chambers. The primary chamber is heated to about 700°C; the coffin containing the body is placed inside, and spontaneous combustion occurs. The temperature increases to 900-1100°C during combustion, which lasts 60-90 minutes if the body is obese or up to 120 minutes if the body is thin or cachectic. The remains are raked down into the secondary chamber to cool. After the cooling process any metal is removed and the residue is crushed to the consistency of coarse sand. This residue weights about 2.0 kg.
Many metal prostheses are implanted in people in Britain: about 40 000 hip replacement operations are performed each year.1 Seventy per cent of the population is cremated (Federation of British Cremation Authorities, personal communication) and only cardiac pacemakers and radioactive implants are removed beforehand. As a result of the Environmental Protection Act 1990 all implants may soon have to be removed before cremations. I studied the scale of this potential problem and why removal may be necessary.
Methods and results
I sent a standard letter about the disposal of implants to 20 crematoriums in Greater London; I subsequently visited six of these. The staff of five of the crematoriums had collected all implants found after cremation for a short period before my visit; the other crematorium had collected a few unexpected metal implants or ingested objects found over the years. The table shows the data that they supplied. Only one crematorium disposed of implants in the general rubbish, a practice that is contrary to the recommendations of the Federation of British Cremation Authorities.
The most common metal residues were hip and knee replacements. Other implanted items collected included intramedullary nails, sliding hip screws, and components from hemiarthroplasties. Less commonly retrieved were McLoughlin nail plates, Jewett nail plates, and Enders nails; one Souttar's tube and one triangular fixation device for hip fractures were also retrieved.2 At one crematorium a substantial number of coins were found: their presence is probably related to social customs in some ethnic groups. The unexpected items found included a variety of forceps (Spencer-Wells, Jean's, and artery), a pacemaker, a ring cutter, a micrometer, and a pair of Mayo scissors.
Comment
The hazards of cremation have been discussed,3 but little work on metal residues after cremation has been published. A study in 1976 of 6000 cremations found that 5% resulted in metal residues.4 In this study 23-76% of cremations resulted in metal residues (table), but this percentage range does not reflect the actual number of bodies with metal residues as one body may have more than one implant. The study shows that implants are common and have increased since 1976.
Data on implants collected for short period by six crematoriums in 1993
As a result of the Environmental Protection Act 1990 the temperature for cremation may have to be raised to 1600°C in the primary chamber to reduce emissions of dioxin.5 All crematoriums will have to comply by 1996. This act has two implications. Firstly, in all the crematoriums I visited the cremating furnace will have to be replaced because the new higher temperatures would damage the existing ovens. Secondly, and of particular concern to the health service, at 1600 degree C stainless steel and cobalt-chrome implants will melt; the melting point for stainless steel is 1290°C and for cobalt-chrome 1350°C (Corin Medical, personal communication). This melting would result in damage to the fire bricks, and because of financial constraints in the public sector the costs of repair might have to be met by health authorities. To avoid this, all implants may have to be removed; this would require logging and tracking, which would be a considerable undertaking and would increase demand on pathology services as on average 42% of all bodies would require intervention.
I thank the management and staff of the six crematoriums visited for their help.