Table 6 Candidate variables used for minimizing Akaike Information Criterion (AIC), via step-AIC algorithm

first

period of first mission to the Chornobyl zone

days_act

duration of active work in the Chornobyl zone in days

Case_leuk

case of leukemia in the study of Zablotska et al. 2013

Year_first_exposed

year first exposed via work in Chornobyl exclusion zone (calculated from dose record)

Year_last_exposed

year last exposed via work in Chornobyl exclusion zone (calculated from dose record)

proxy^a

proxy interviews

proxy_str

proxy status based on the cases status in the set

number1

number of missions

first_year

year first exposed via work in Chornobyl exclusion zone

duration

total duration of work in the Chornobyl zone in months

duration_act

duration of active work in the Chornobyl zone in months

days

total duration of work in the Chornobyl zone in days

tse

time since first exposure in the zone until diagnosis (for cases) and reference time (for controls) in years; tse < 0 (n = 4) is set to 0

radiation

non-Chornobyl work with radiation exposure

industry

work in hazardous industries

oil

oil or chemical industry

chemical

non-Chornobyl work with hazardous chemicals

petroleum

work in petroleum industry

pesticides

work with pesticides

solvents

work with solvents

other_chemical

work with hazardous chemicals other than in petroleum industry/pesticides/solvents

age

age at diagnosis (for cases) and age at reference date (for controls)

age_x

age at first exposure in the zone

subtype^a

subtype of leukemia

subtypecll^a

CLL subtype

subtypecll_str

CLL subtype, based on the case status, matching controls set to case status

y_dx^a

year of diagnosis; for controls set to −1

reference

reference year set to year of diagnosis (for cases) and for controls is the same as for matched case

y_int

year of interview

liqtype

type of work performed in the Chornobyl zone during the first mission

flag1

additional controls re-distributed among cases

flag2

controls used in risk analysis for Phase I but now matched to their original case used in set Phase II

flag_definite

certainty in the leukemia diagnosis (definite + probable/other)

Phase

study phase (phase I/phase II)

COM1_EXP1

dosimetry expert’s opinion about the quality of interview during the 1st mission to the 30-km exclusion zone

COM2_EXP1

dosimetry expert’s opinion about the quality of interview during the 2nd mission to the 30-km exclusion zone

COM3_EXP1

dosimetry expert’s opinion about the quality of interview during the 3rd mission to the 30-km exclusion zone

QUES1

interviewer’s opinion on the quality of questionnaire: Did subject reply with interest?

QUES2

interviewer’s opinion on the quality of questionnaire: Did the worker remember his job in the 30-km exclusion zone?

Liquid

clean-up worker with data on interviewer’s opinion about the quality of interview

Exp

expert dosimetrist who prepared dosimetric questionnaire for input into RADRUE

time_int_ch

time from interview to chemotherapy (date of start of chemotherapy for CLL and date of diagnosis for non-CLL)

set^a

cases with direct interviews

t11^a

if time_int_ch ≠ 99 and time_int_ch ≠ −1 and cases = 1 and proxy = 0 and −1 ≤ time_int_ch ≤ 1 then t11 = 1;else t11 = 0;

t1515^a

if time_int_ch ≠ 99 and time_int_ch ≠ −1 and cases = 1 and proxy = 0 and −1.5 ≤ time_int_ch ≤ 1.5 then t1515 = 1;else t1515 = 0;

t12^a

if time_int_ch ≠ 99 and time_int_ch ≠ −1 and cases = 1 and proxy = 0 and −1.0 ≤ time_int_ch ≤ 2.0 then t12 = 1;else t12 = 0;

t22

if time_int_ch ≠ 99 and time_int_ch ≠ −1 and cases = 1 and proxy = 0 and −2.0 < time_int_ch < 2.0 then t22 = 1; else t22 = 0

liqtype_recode

type of work performed in the Chornobyl zone during the first mission recoded (from liqtype) (missing/early responders & firefighters/professional nuclear power workers/military personnel/drivers & construction workers)

num_miss

number of missions to the Chornobyl exclusion zone

rad_exp

study subject ever worked with radiation (other than the time the study subject spent in the Chornobyl area)

rad_radiography

study subject ever worked with radiation as industrial radiographer (other than time study subject spent in the Chornobyl area)

rad_nuclear

study subject ever worked with radiation in the nuclear industry (including NPP, other than time the study subject spent in the Chornobyl area)

rad_army

study subject ever worked with radiation in army service (other than time the study subject spent in the Chornobyl area)

rad_other

study subject ever worked with radiation other than in army/nuclear industry/industrial radiography (other than time the study subject spent in the Chornobyl area)

haz_exp

study subject ever worked in a hazardous industry (specific types of chemical/electrical/road-building/other)

haz_chem

study subject worked in chemical industry/oil industry (hazardous industry)

haz_el

study subject worked in electrical industry (hazardous industry)

haz_road

study subject worked in road-building industry (hazardous industry)

haz_other

study subject worked in one of coal mining/military service/metallurgical industry/welding/gas equipment/other hazardous industries (hazardous industry)

chem_exp

Has the study subject ever worked with hazardous chemicals?

chem_petrol

study subject worked with petrol (petrol and agricultural pesticides/petrol and organic solvents)

chem_pest

study subject worked with agricultural pesticides (petrol and agricultural pesticides/agricultural pesticides and organic solvents/agricultural pesticides and other)

chem_solv^a

study subject worked with organic solvents (petrol and organic solvents/agricultural pesticides and organic solvents)

chem_other

study subject worked with hazardous chemical other than petroleum/agricultural pesticides/organic solvents

Oblast

Dnipropetrovsk/Kyiv oblast/Kharkiv/Cherkassy/Chernihiv/Kyiv-city

Educ

level of education of interviewee (8 years or less school/high school/trade school/higher education)

Urban

Type of settlement (city/village/other)

radtx^a

Has the study subject had radiotherapy for cancer treatment

chemotx^a

Has study subject had chemotherapy for cancer treatment

radtx_other

Has the study subject ever received radiotherapy for medical conditions other than cancer

x_dental

Has study subject ever had dental X-ray?

x_dental_n

Number of times study subject has had dental X-ray

x_bone

Has interviewee ever had bone X-ray?

x_bone_n

Number of times interviewee has had bone X-ray?

x_chest

Has study subject ever had chest X-ray (except fluoroscopy)

x_chest_n

Number of times study subject ever had chest X-ray (except fluoroscopy)

x_other

Has the interviewee ever had other X-ray examinations (than bone, chest, dental)?

x_other_n

How many times interviewee had any other type (than bone, chest, dental) of X-ray examination?

fam_cancer

Have any of interviewee’s relatives had any solid cancer or leukemia (mother or father, or other relative)?