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Ethnic differences in blood lead concentration among workers in a battery manufacturing factory

Chia SE, Chia KS, Ong CN

Ann Acad Med Singap, 1991 Nov;20(6):758-61.
PMID: 1803964

Blood lead levels of two ethnic groups (11 Chinese and 25 Malays) of workers in a factory manufacturing lead accumulator battery were studied. The mean adjusted (for environmental lead levels, age, exposure duration and stick-years of smoking by analysis of covariance) blood lead level of the Malays was 34.8 micrograms/dl as compared to 22.4 micrograms/dl for the Chinese. This difference was significant (p less than 0.02). Oral ingestion of lead, through eating of food with hands contaminated by lead compound, among the Malay workers was suggested as a possible cause for the difference in the mean blood lead levels. Preventive measures and recommendations to overcome the problem among this particular group of workers were discussed.
Pulmonary function in healthy Chinese, Malay and Indian adults in Singapore

Chia SE, Wang YT, Chan OY, Poh SC

Ann Acad Med Singap, 1993 Nov;22(6):878-84.
PMID: 8129348

Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), peak expiratory flow rate (PEFR), single-breath diffusion capacity measurements (effective alveolar volume (VA), carbon monoxide transfer factor (DLCO) and transfer coefficient (KCO)) were determined in 452 healthy Singaporean adults (277 males and 175 females) aged 20-70 years. The ratio of Chinese, Malay and Indian subjects was 5:2:3 in both sexes. Age, height and weight in the males were all significantly correlated with FEV1, FVC, DLCO, VA and PEFR. However, for females, only age and height were significantly correlated with the studied lung function parameters. Significant ethnic differences were observed for most of the pulmonary functions (except KCO and PEFR) among the Chinese, Malays and Indians for both males and females. The predicted FEV1 and FVC values (specific age and height) for both sexes were highest among the Chinese followed by the Malays than Indians, in that order. Regression equations, with age and height as independent variables, were derived for males and females in each ethnic group to predict normal pulmonary function for the Singapore Chinese, Malay and Indian populations. The predicted values of various pulmonary function measurements obtained from these regression equations for subjects of specified age (30 years) and height (165 cm for men, 155 cm for women) were compared with those reported in other studies. Differences were observed among the different races.
Sun exposure and the risk of prostate cancer in the Singapore Prostate Cancer Study: a case-control study

Chia SE, Wong KY, Cheng C, Lau W, Tan PH

Asian Pac J Cancer Prev, 2012;13(7):3179-85.
PMID: 22994730

BACKGROUND: Most of the epidemiology studies on the effects of sun exposure and prostate cancer were conducted among the temperate countries of North America and Europe. Little is known about the influence on Asian populations. The purpose of current study was to evaluate any association of sun exposure with risk of prostate cancer in Chinese, Malays and Indians who reside in the tropics.
METHODS: The Singapore Prostate Cancer Study is a hospital-based case-control study of 240 prostate cancer incident cases and 268 controls conducted in Singapore between April 2007 and May 2009. Detailed information on outdoor activities in the sun, skin colour, sun sensitivity and other possible risk factors were collected in personal interviews. Cases were further classified by Gleason scores and TNM staging. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using unconditional logistic regression analysis, adjusted for age, ethnicity, education, family history of any cancers, BMI and skin colour.
RESULTS: We found that prostate cancer risk was increased in subjects with black/dark-brown eyes (OR 5.88, 95%CI 3.17-10.9), darker skin colour e.g. tan/dark brown/black (OR 7.62, 95%CI 3.41-17.0), frequent sunburn in lifetime (OR 4.30, 95%CI 1.7-11.2) and increased general sun exposure in adulthood per week (OR 2.03, 95%CI 1.09-3.81). The increased risk was consistent for high grade tumours and advanced stage prostate cancers.
CONCLUSION: The findings from this study suggest that excessive sun exposure is a risk factor for prostate cancer in Asians.
Distribution of PON1 polymorphisms PON1Q192R and PON1L55M among Chinese, Malay and Indian males in Singapore and possible susceptibility to organophosphate exposure

Chia SE, Mohamed Ali S, Yap PH, Gan L, Ong YB, Chia KS

Neurotoxicology, 2009 Mar;30(2):214-9.
PMID: 19135476 DOI: 10.1016/j.neuro.2008.12.004

Organophosphate (OP)-containing pesticides are widely used worldwide for domestic and industrial purposes. Studies on acute and chronic exposure to OPs have revealed numerous health effects attributed mainly to acetylcholinesterase (AChE) inhibition. The enzyme human serum paraoxonase (PON1) is involved in the detoxification of OP compounds. PON1 polymorphisms have been shown to affect susceptibility to OP exposure. We studied the effect of OP exposure on pest control workers and assessed the distribution of two common PON1 polymorphisms in our local population. The exposed group consisted of 103 workers from various pest control companies under the Singapore Pest Management Association while the 91 unexposed workers were from a lead stabilizer factory. For all workers, the mean age was 36.9 (20-70) years and the ethnic distribution was 38.1% Chinese, 44.3% Malay and 17.5% Indian. The mean+/-S.D. exposure duration among the pesticide workers was 10.4+/-8.4 years. The mean+/-S.D. RBC cholinesterase level was 18436.2+/-2078U/L and 18079.6+/-1576U/L for the exposed and unexposed groups, respectively (p=0.216). The mean+/-S.D. serum pseudocholinesterase was 11028.4+/-2867.4U/L and 9433.6+/-2022.6U/L in the exposed and unexposed groups, respectively (p<0.0001). Mean paraoxonase activity was similar among Chinese and Malays (266.5 and 266.3U/L, respectively) whereas that of the Indians was significantly lower (165.6U/L). Our study showed that cholinesterase levels among the exposed were not lower than those in the unexposed group. PON1 polymorphisms differed among ethnic groups, implying that ethnicity could be an important surrogate for identifying susceptible groups in case of OP exposure. Although OP poisoning is rare among occupationally exposed workers in Singapore, this information is useful for other developing countries that have large populations of Chinese, Malays and Indians where OP exposure could be very high especially in agricultural settings.
Fulltext Prostate-specific antigen levels among Chinese, Malays and Indians in Singapore from a community-based study

Chia SE, Lau WK, Cheng C, Chin CM, Tan J, Ho SH

Asian Pac J Cancer Prev, 2007 Jul-Sep;8(3):375-8.
PMID: 18159971

The purpose of this study was to examine the distribution of prostate-specific antigen levels among Chinese, Malays and Indians in Singapore, taking the effect of age into consideration. The study was carried out as part of the Singapore Prostate Awareness Week from 23-26th February 2004. Men above 50 years old went to four government-restructured hospitals to participate in the study. Participants filled up a questionnaire and provided 5 ml of blood for measurement of PSA levels using the Abbott IMx Total PSA assay (Abbott Laboratories). 3,486 men responded to the study, comprising 92.8% Chinese, 3.0% Malays, 2.5% Indians and 1.8% Others. 92.7% of them had PSA levels of 4 microg/L or less. There were no significant differences (p<0.05) between the mean PSA levels of Chinese (1.60 microg/L), Malays (1.39 microg/L), Indians (1.23 microg/L) and Others (1.70 microg/L). PSA levels were significantly associated with age (Spearman's r= 0.27, p<0.01). PSA levels increased with each 10-year age group and these trends were significant (p<0.0001) across both PSA group levels and age groupings. In the 50-60 years age groups, the prevalence of PSA levels >4 mug/L were 1.1% and 3.7% respectively. This rose rapidly to 11.3% and 23.5% for age groups >60-70 and >80 years respectively. Our study shows that the median PSA levels in the Caucasian population in the USA are higher than those of Chinese, Malays and Indians in Singapore. PSA levels were positively associated with age. It may be more appropriate to offer PSA testing to men who are >60 years old rather than the current >50 years.
8q24 and 17q prostate cancer susceptibility loci in a multiethnic Asian cohort

Chan JY, Li H, Singh O, Mahajan A, Ramasamy S, Subramaniyan K, et al.

Urol Oncol, 2013 Nov;31(8):1553-60.
PMID: 22561070 DOI: 10.1016/j.urolonc.2012.02.009

OBJECTIVES: Recently, several genome-wide association studies have demonstrated a cumulative association of 5 polymorphic variants in chromosomes 8q24 and 17q with prostate cancer (CaP) risk in Caucasians, particularly those harboring aggressive clinicopathologic characteristics. The purpose of this study was to evaluate the influence of these variants on CaP susceptibility in Singaporean Asian men.
MATERIALS AND METHODS: We performed a case-control study in 289 Chinese CaP patients and 412 healthy subjects (144 Chinese, 134 Malays, and 134 Indians), and examined the association of the 5 single nucleotide polymorphisms (SNPs) with CaP.
RESULTS: In the healthy subjects, rs16901979 A-allele frequency was highest amongst Chinese (0.32) compared with Malays (0.13; P < 0.0001) or Indians (0.09; P < 0.0001); rs6983267 G-allele was highest in Indians (0.51) compared with Chinese (0.42; P = 0.041) or Malays (0.43; P = 0.077); whereas rs1859962 G-allele frequency was highest amongst Indians (0.56) compared with Chinese (0.40; P = 0.0002) or Malays (0.38; P < 0.0001). Individuals with the rs4430796 TT genotype were at increased CaP risk in the Chinese via a recessive model (odds ratios (OR) = 1.56, 95% CI = 1.04-2.33). Significant associations were observed for rs4430796 TT with Gleason scores of ≥ 7 (OR = 1.76, 95% CI = 1.14-2.73) and prostate-specific antigen (PSA) levels of ≥ 10 ng/ml at diagnosis (OR = 1.63, 95% CI = 1.01-2.63), as well as for rs6983267 GG with stage 3-4 CaPs (OR = 1.91, 95% CI = 1.01-3.61). A cumulative gene interaction influence on disease risk, which approximately doubled for individuals with at least 2 susceptibility genotypes, was also identified (OR = 2.18, 95% CI = 1.10-4.32).
CONCLUSIONS: This exploratory analysis suggests that the 5 genetic variants previously described may contribute to prostate cancer risk in Singaporean men.
KEYWORDS: Cancer; Ethnicity; Gleason; Pharmacogenetics; Polymorphism; Prostate