2. Material and methods
2.1. Exposure assessment
Lead exposure was estimated based on data
from the Blood Lead Register in terms of a
Cumulative Blood Lead Index ŽCBLI., which is
calculated through a summation of the individual’s
annual mean blood lead values ŽB-Pbs.. Since
1950, lead in whole blood has been regularly
monitored at the smelter. For the analysis, emission
spectrometry was used from 1950 to 1969. It
was gradually exchanged for atomic absorption
spectrometry since 1967. The two methods were
thus used in parallel for a few years with good
agreement. A thorough description of sampling,
analysis and quality control programs has previously
been presented ŽLundstr¨om et al., 1997..
Arsenic exposure, mainly via inhalation, was
assessed in detail in the lung cancer cases of the
subcohorts Žsee below. based on detailed information
in company occupational records and from
spot air sampling undertaken by the company
health service.
It is not possible here to give a detailed account
of air concentrations of arsenic and other
chemical compounds at the smelter over the years
but a few examples will be given. Dust sampling
at fixed sampling stations was occasionally made
since the early 1940s and thereafter gradually
extended. Airborne lead levels could exceed 1
mgm3 at the lead plant in the 1940s. Sulfur
dioxide levels ranged from 70 to 560 mgm3
Žmean 220 mgm3. at the roasters during the
1940s. The SO2 levels in 1945 were approximately
20 times higher than during the period 19581964
when they decreased to 510 mgm3 ŽLundstr¨om
et al., 1997.. At the end of the 1940s concentrations
of airborne arsenic ranged from 0.35 to 1.5
mgm3 at the roasters and were somewhat lower
at the arsenic department. Exposure to arsenic
among workers in the arsenic department and at
the roasters has been estimated to be close to the
Swedish occupational exposure limit which was
500 gm3 from the 1940 and up to 1975 and 50
gm3 from 1975 to 1987 ŽLagerkvist et al., 1986..