A case control study of exposure to radon in the home in Cornwall and Devon and lung cancer is being carried out in order to provide a more precise estimate of the risk of lung cancer from exposure in the home.
In 5 study centres (Truro, Plymouth, Barnstaple, Torquay, and Exeter) a total of 1839 patients with suspected lung cancer have been identified to date. 178 patients (9.7%) were too ill to be approached for interview and, of the remainder, 60 (3.6%) refused to take part. 741 patients had not lived in Devon or Cornwall for long enough to satisfy residence requirements, and 859 patients received a full interview.
Review of hospital discharge diagnoses has been carried out for 715 of the 859 patients with suspected lung cancer who received a full interview. For 475 (66.4%) the final diagnosis was lung cancer. In about 96% of those for whom the final diagnosis was lung cancer an attempt was made to obtain a microscopic diagnosis. For 67% the diagnosis of lung cancer was confirmed by histology, and for a further 11% the lung cancer was confirmed by cytology alone.
Review of the hospital discharge diagnoses has been carried out for 689 of the 772 hospital controls with full interview. For 21 patients the final diagnosis rendered them ineligible as controls, as they turned out to have diseases strongly related to smoking.
To date 1018 potential community controls have been selected from the Family Health Services Authority (FHSA) lists, and processing is complete for 905. 404 have recieved a full interview.
At the present time Devon FHSA have refused to supply any further names on the grounds that to do so would be a breach of confidentiality, and this poses a serious threat to the continued smooth operation of the study.
Of the 2035 cases, hospital controls and community controls who have received a full interview, the interviewers have reported that a detector has been successfully installed in the homes of 1806 (94.8%). Attempts will be made to mea sure radon concentrations in the current homes of subjects and also in their previous homes in Cornwall and Devon during the last 35 years.
RADON IN HOUSES IS ONE OF THE MOST IMPORTANT SOURCES OF RADIATION EXPOSURE TO WHICH THE GENERAL PUBLIC IS SUBJECT. ACCORDING TO THE LATEST ESTIMATES MADE BY THE NATIONAL RADIOLOGICAL PROTECTION BOARD, THE CONTRIBUTION OF RADON DAUGHTERS IN THE UK IS AROUND 50% OF THE AVERAGE ANNUAL EFFECTIVE DOSE EQUIVALENT. THE PRINCIPAL PARTS OF THE BODY AFFECTED ARE THE BRONCHI WHERE RADIONUCLIDES EMITTING ALPHA PARTICLES ARE LIABLE TO BE DEPOSITED.
EXTRAPOLATION FROM THE EXPERIENCE OF THESE MINING POPULATIONS SUGGESTS THAT THIS SOURCE OF RADIATION MAY BE RESPONSIBLE FOR A FEW PER CENT OF ALL THE CASES OF LUNG CANCER THAT OCCUR IN THE COUNTRY EACH YEAR. THE AMOUNT OF RADIATION, HOWEVER, VARIES FROM HOUSE TO HOUSE, PARTLY BECAUSE OF THE PHYSICAL CHARACTERISTICS OF THE HOUSE, INCLUDING THE WAY IT WAS BUILT AND IS VENTILATED, BUT MAINLY BECAUSE OF VARIATION IN THE NATURAL RADIOACTIVITY AND PERMEABILITY OF THE SOIL ON WHICH THE HOUSE IS BUILT. THIS VARIATION IS SO GREAT THAT SOME HOUSEHOLDERS RECEIVE SUCH HIGH DOSES THAT REMEDIAL AND PREVENTIVE MEASURES HAVE BEEN INTRODUCED FOR HOUSES.
IT IS PROPOSED, THEREFORE, TO INTERVIEW PEOPLE IN CORNWALL AND DEVON, WHERE SURVEYS HAVE SHOWN THAT THERE IS A WIDE VARIATION IN RADON CONCENTRATION OWING TO THE PRESENCE OF A SUBSTANTIAL PORTION OF HOUSES WITH RELATIVELY HIGH CONCENTRATIONS OF RADON AND ALSO AREAS WITH LOW CONCENTRATIONS. A STANDARD QUESTIONNAIRE WOULD BE USED AND PEOPLE IN THE FOLLOWING CATEGORIES WOULD BE INTERVIEWED:
(I) PATIENTS UNDER 75 YEARS OF AGE WITH A PRESUMPTIVE DIAGNOSIS OF LUNG CANCER AND MOST OF WHOM WOULD BE ADMITTED TO HOSPITAL,
(II) AN AGE/SEX MATCHED SAMPLE OF PATIENTS ADMITTED TO THE SAME HOSPITALS WITH PRESUMPTIVE DIAGNOSIS OF A WIDE VARIETY OF CONDITIONS UNRELATED TO SMOKING, AND
(III) AN AGE/SEX MATCHED SAMPLE OF COMMUNITY CONTROLS CHOSEN AT RANDOM FROM FAMILY PRACTITIONER COMMITTEE LISTS FOR DEVON AND CORNWALL.
THE PROPOSAL IS MADE TO INTERVIEW PATIENTS WITH VARIOUS PRESUMPTIVE DIAGNOSIS RATHER THAN WITH CONFIRMED DIAGNOSIS FOR TWO REASONS. FIRST IT PROVIDES MORE OPPORTUNITIES TO SEE THE PATIENTS WHILST THEY ARE STILL IN OR ATTENDING HOSPITAL AND AVAILABLE FOR INTERVIEWING AND SECONDLY BECAUSE WHEN FINAL DIAGNOSIS ARE CHECKED AFTER DISCHARGE, THE GROUP OF PATIENTS WHOSE DIAGNOSIS HAVE BEEN CHANGED PROVIDES EXCEPTIONALLY VALUABLE CONTROL FREE OF ANY POSSIBLE INTERVIEWING BIAS THAT MIGHT BE ASSOCIATED WITH KNOWLEDGE OF THE NATURE OF THE DISEASE.
THE RESIDENTIAL HISTORIES OBTAINED FROM THE INTERVIEWS WILL ENABLE A LIST OF HOUSES TO BE PREPARED IN WHICH MEASUREMENTS OF RADON CONCENTRATIONS CAN SUBSEQUENTLY BE MADE, IN ORDER TO BUILD UP A PICTURE OF THE RADIATION EXPOSURE OF EACH PERSON IN THE STUDY. TWO MEASUREMENTS WILL BE MADE IN EACH HOUSE FOR AN EXTENDED PERIOD AND ANNUAL EXPOSURES WILL BE ESTIMATED.
INDIVIDUALS WILL BE INCLUDED ONLY IF THEY WERE BORN IN CORNWALL OR DEVON OR, OF A PILOT STUDY SHOWS THAT THIS WOULD SERIOUSLY REDUCE THE NUMBER OF LONG CANCER PATIENTS, IF THEY HAD FIRST LIVED IN ONE OR OTHER COUNTY BEFORE (SAY) 15 YEARS OF AGE.
IT IS HOPED THAT IT WILL BE POSSIBLE TO INTERVIEW BETWEEN 500 AND 1000 PATIENTS WITH LUNG CANCER IN THE COURSE OF THREE YEARS AND TWICE THAT NUMBER OF CONTROL SUBJECTS. RADON MEASUREMENTS AND DATA ANALYSES WILL EXTEND INTO A FOURTH YEAR.
FROM THE VARIOUS SETS OF DATA OBTAINED IN THIS WAY IT WILL THEN BE POSSIBLE TO ESTIMATE RELATIVE RISKS FOR DIFFERENT DEGREES OF EXPOSURE, STANDARDIZED FOR SEX, AGE, SMOKING HABITS, AND OCCUPATION.