Evacuation decisions in a chemical air pollution incident: cross sectional survey.

OBJECTIVE: To compare the health outcomes in sheltered and evacuated populations after a chemical incident in a plastics factory. DESIGN: Cross sectional survey. SETTING: Urban area in southwest England. PARTICIPANTS: 1750 residents from the area exposed to the chemical smoke, of which 472 were evacuated and the remaining 1278 were advised to shelter indoors. MAIN OUTCOME MEASURE: Number of adverse health symptoms. A case was defined by the presence of four or more symptoms. MAIN RESULTS: 1096 residents (63%; 299 evacuated, 797 sheltered) provided data for analyses. The mean symptom score and proportion of cases were higher in evacuated people than in the sheltered population (evacuated: symptom score 1.9, cases 19.7% (n = 59); sheltered: symptom score 1.0, cases 9.5% (n = 76); P < 0.001 for both). The difference between the two groups attenuated markedly at the end of two weeks from the start of the incident. The two main modifiable risk factors for the odds of becoming a case were evacuation (odds ratio 2.5, 95% confidence interval 1.7 to 3.8) and direct exposure to smoke for more than two hours on the first day of the incident (2.0, 1.7 to 2.3). The distance of residence from the factory or level of exposure before intervention (first six hours) had little effect on the odds of a person becoming a case. CONCLUSIONS: Sheltering may have been a better protective action than evacuation in this chemical incident, which is consistent with the prevailing expert view. Although this study has limitations, it is based on a real event. Evacuations carry their own risks and resource implications; increased awareness may help to reduce unnecessary evacuations in the future.

Inter-rater agreement in defining chemical incidents at the National Poisons Information Service, London.

BACKGROUND: National surveillance for chemical incidents is being developed in the UK. It is important to improve the quality of information collected, standardise techniques, and train personnel. OBJECTIVE: To define the extent to which eight National Poison Information Service specialists in poison information agree on the classification of calls received as "chemical incidents" based on the national definition. DESIGN: Blinded, inter-rater reliability measured using the kappa statistic for multiple raters. SETTING: National Poison Information Service and Chemical Incident Response Service, Guy's and St Thomas's NHS Trust, London. PARTICIPANTS: Eight specialists in poison information who are trained and experienced in handling poisons information calls and have been involved in extracting information for surveillance. RESULTS: The overall level of agreement observed was at least 69% greater than expected by chance (kappa statistic). Fire and incidents where chemicals were released within a property had a very good level of agreement with kappa statistic of 83% and 80% respectively. The lowest level of agreement was observed when no one or only one person was exposed to a chemical (33%) and when the chemical was released into the air (48%). CONCLUSION: High levels of agreement were observed. There is a need for more training and improvement in consistency of the data collected by all organisations.