Int. J. Environ. Res. Public Health 2009, 6 1001 41 men were engaged in logistics and the rest of them were engaged in office work. The mean age, and body mass index (BMI) were 43.4±11.9 years and 23.4±4.13 kg/m2 (mean ± SD), respectively. 2.2. Basic Characteristics and Blood Measurements Age and smoking status were self-reported. The medical and occupational histories were established by interview. Height, weight, systolic and diastolic blood pressures were measured by trained staff nurses. BMI was calculated as weight by height square (kg/m2). The blood samples of all participants were taken by trained staff nurses and the withdrawn blood samples were kept in the plain tubes for examining fasting blood glucose, serum lipids (total cholesterol, triglyceride, HDL cholesterol), aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transpeptidase (γ-GTP), blood urea nitrogen (BUN), serum creatinine (Cr), serum uric acid (UA), blood lead concentration, and biomarkers for lead exposure (serum and urinary 5-aminolevulinic acid; sALA and uALA, and Zinc protoporphyrin; ZnPP). Blood lead concentration was measured by flameless atomic absorption spectrophotometry (Hitachi Z-9000) with Zeeman effect background correction. To determine delta-aminolevulinic acid levels (sALA in serum and uALA in urine) and Zinc protoporphyrin (Znpp) in blood, we used a type L-6200 HPLC (Hitachi, Japan). Using this apparatus, stopped-flow HPLC was applied to determine these parameters using a reverse phase column after a simple pretreatment. The highest fluorescent intensity was obtained when the pretreated sample was doubly diluted with 100 mM sodium acetate (pH 5.0), and the sample (60 μL) was introduced into the condensing coil at a temperature of 98 °C, then 50% acetylacetone in 25% ethanol was added, followed by secondary mixing with 10% formaldehyde solution. The detection limit was 2 μg/L, which was 2.5 times higher than that achievable by conventional method. Relative standard deviations of 10 blood samples calculated from 4 determinations per sample for 1 week were within 5%. Haemoglobin was determined by the cyanomethaemoglobin method. 2.3. Genotyping The peripheral blood from all participants were drawn, and genotyping for the ALAD polymorphism (a single nucleotide polymorphism database, dbSNP ID: rs1800435 referenced information from NCBI, and the International HapMap Project) was performed by polymerase chain reaction (PCR) and the single nucleotide primer extension (SNuPe) methods. The blood was pretreated with Ampdirect (SHIMADZU Corporation, Kyoto, Japan), which could eliminate the DNA extraction process and amplify the genomic DNA directly from the whole blood. PCR primers 5’ - GGCCTCAGTCTTCCCTCCTA -3’ (sense) and 5’ -ACCTCTCCACCTCCCGAGTA -3’ (antisense) as