2 within a day. These blood specimens were stored at −20◦C until use for the measurements of fatty acid compositions and the total mercury concentrations. Methyl-esteriﬁed fatty acids from either the total serum or the serum high-density lipoprotein (HDL) fractions sep- arated from the total serum by the precipitated method of dextran sulphate Mg++ [9] were analyzed by gas liquid chro- matography on 5% Shinchrome E71 [10]. EPA (C 20:5) in the total serum was measured. EPA was also measured in the serum HDL fraction to examine its long-term consumption. Serum EPA was 64.5 mg/L. EPA in HDL fraction was 26.2 mg/L. Therefore, 40.6% of EPA would be included in HDL fraction. Total mercury concentration of RBC was measured by the cold vapor atomic absorption spectrometry after wet dig- estion in 2.5 mL sulfuric acid and 1 mL mixture of nitric and perchloric acids (5:1:1) at 250◦C for 20 minutes [11]. Quality control of mercury analysis was conducted by comparing with the analysis of reference standard (e.g., IAEA085 and 086). Calibration of fatty acid measurements was conducted by comparison with the relative retention time of each fatty acid to septadecanoic acid (C 17:0, 100 mg/L), which was used as an internal standard on GC. Authentic fatty acid- methyl esters were obtained from ﬁsh oil on silica-gel thin- layer chromatograph impregnated 20% of silver nitrate by hexane-ethyl-ether (90:10) as a solvent system. Each authen- tic fatty acid was analyzed on GC with C 17:0 to obtain each relative retention time to C 17:0. 3. Statistical Analysis Geometric means and corresponding 95% conﬁdence inter- vals for the concentrations of total mercury in RBCs (RBC Hg) and EPA in the serum were calculated. Univariate and multivariate regression analyses were conducted by the intercooled Stata 8.1. Since the distributions of RBC Hg and EPA were skewed and had a long upper tail, log-transformed values were used in these analyses. Trend of association was assessed by regression models assigning consecutive integers to the levels of the independent variable or treating the in- dependent variable as a continuous variable as described in the foot notes of each table. 4. Results The subjects examined in the present study are 98 men and 171 women. Their age distributions are shown in Table 1. Sex and age-speciﬁc levels of RBC Hg and serum EPA are sum- marized in Table 1 as well. The RBC-Hg level decreased with age among men (P < 0.001) but not among women (P = 0.114). Serum concentrations of EPA also decreased with age among men (P = 0.001) but less evidently among women (P = 0.070). The EPA levels in the HDL fraction of sera were also examined. Age dependence was much less evident and not statistically signiﬁcant among men or women. RBC Hg levels were related to the frequencies of ﬁsh con- sumption in a week (P = 0.035) obtained from the interview among women but not among men (P = 0.643) as shown in Table 2. However, such a relationship was not observed Journal of Environmental and Public Health among men. On the other hand, the serum level of EPA, which is considered to be almost exclusively derived from ﬁsh consumption, was not related to ﬁsh consumption among men (P = 0.207) or women (P = 0.582). However, the EPA level in the HDL fraction of the serum increased with ﬁsh consumption among both men (P = 0.014) and women (P = 0.073). The association between the levels of serum EPA and RBC Hg was examined (Table 3). Serum EPA levels were related to RBC mercury levels among women (P = 0.005) but not among men (P = 0.149). In contrast, serum EPA levels in the HDL fraction of the serum were also signiﬁcantly related to RBC mercury levels among women (P = 0.001) but not among men (P = 0.568). Although the questionnaire used in our interview survey did not include questions of ﬁsh species, processing methods (raw ﬁsh, ﬁsh paste products, or dry ﬁsh) were asked. Men tended to consume more dry ﬁsh than women did although the diﬀerence was not statistically signiﬁcant (Table 4). 5. Discussions The total daily amount of mercury intake is known to be strongly related to the amount of ﬁsh consumption [12, 13]. The ﬁsh consumption, which was measured directly or by using food frequency questionnaires, was related to EPA concentrations in RBC [14–16]. In the present study, RBC Hg concentrations were related to ﬁsh consumption among women but not among men. Only a limited number of studies examined the associa- tion of serum EPA and mercury levels with ﬁsh consumption. Innis et al. reported that RBC EPA levels were related to blood mercury levels among children with relatively low mercury levels [17], but this association became unclear when blood mercury levels were 28.9 nmol/L or higher. In the present study, neither among men nor among women, serum EPA level was related to weekly ﬁsh consumption even though ﬁsh consumption is the only source of serum EPA. However, the EPA level in the HDL fraction of the serum increased with ﬁsh consumption in both men and women. The con- centrations of triglycerides in plasma increased signiﬁcantly after the meal and fell below fasting levels by 9 and 12 hours [18]. In the contrast, the major HDL apolipoproteins are apo A-I and apo A-II, and both are required for normal HDL biosynthesis [19]. The turnover of apo A is considered to have a turnover rate of about 4 days [20]. On the other hand, the major protein component of low-density lipoprotein and very-low-density lipoprotein is apolipoprotein B, whose turnover is much shorter than 4 days [21, 22]. Therefore, EPA level in HDL fraction was related more strongly to weekly ﬁsh consumption while total serum EPA reﬂects much more recent dietary intake. Fish consumption was related to only HDL-EPA levels in our study. So we suspected that our questionnaire reﬂected long-term ﬁsh consumption. In addition, the relationship between Hg levels in RBC and HDL EPA levels was stronger than the association of RBC Hg levels with serum EPA levels. After entry, mercury stays on in RBCs during their life span, which is 120 days on average [23–25], and, therefore, Hg levels in RBC may be