Risk assessment for Thai population: benchmark dose of urinary and blood cadmium levels for renal effects by hybrid approach of inhabitants living in polluted and non-polluted areas in Thailand.

Muneko Nishijo,Hideaki Nakagawa,Witaya Swaddiwudhipong,Kazuhiro Nogawa,Kowit Nambunmee,Yasushi Suwazono,Werawan Ruangyuttikarn

doi:10.1186/1471-2458-14-702

Abstract

BackgroundThe aim of the present study was to estimate the benchmark doses (BMD) for renal effects for health risk assessment of residents living in Cd-polluted and non-polluted areas in a Thai population.MethodsThe study participants consisted of inhabitants aged 40 years or older who lived in a non-polluted area (40 men and 41 women) and in the environmentally polluted Mae Sot District (230 men and 370 women) located in northwestern Thailand. We measured urinary and blood cadmium (Cd) as markers of long-term exposure and urinary β2-microglobulin (β2-MG) and N-acetyl-β-D-glucosaminidase (NAG) as renal tubular effect markers. An updated hybrid approach was applied to estimate the benchmark doses (BMD) and their 95% lower confidence limits (BMDL) of urinary and blood Cd for Cd-induced renal effects in these subjects. BMD and BMDL corresponding to an additional risk (BMR) of 5% were calculated with the background risk at zero exposure set to 5% after adjusting for age and smoking status.ResultsThe estimated BMDLs of urinary Cd for renal effect markers were 6.9 for urinary β2-MG and 4.4 for NAG in men and 8.1 for β2-MG and 6.1 for NAG μg/g creatinine (Creat) in women. These BMDLs of urinary Cd (μg/g Creat) for NAG were less than the geometric mean urinary Cd in the polluted area (6.5 in men and 7.1 in women). The estimated BMDLs of blood Cd (μg/L) were 6.2 for urinary β2-MG and 5.0 for NAG in men and 5.9 for β2-MG and 5.8 for NAG in women. The calculated BMDLs were similar or less compared with the geometric mean blood Cd (μg/L) in the polluted Thai area (6.9 in men and 5.2 in women).ConclusionThe BMDLs of urinary and blood Cd for renal effects were estimated to be 4.4 - 8.1 μg/g Creat and 4.4 - 6.2 μg/L in the Thai population aged ≥ 40 years old, suggesting that more than 40% of the residents were at risk of adverse renal effects induced by Cd exposure in Thailand.

Highlights

The aim of the present study was to estimate the benchmark doses (BMD) for renal effects for health risk assessment of residents living in Cd-polluted and non-polluted areas in a Thai population
The BMD is defined as the exposure level that corresponds to a specific increase in the probability of an adverse response, compared with the response at zero background exposure
The statistical validity and efficiency of the BMD and BMDL values were greater using the hybrid approach compared with methods involving categorization of continuous exposure and effect markers

Summary

Introduction

The aim of the present study was to estimate the benchmark doses (BMD) for renal effects for health risk assessment of residents living in Cd-polluted and non-polluted areas in a Thai population. As a health risk assessment of Cd exposure, several studies in the Japanese population have applied the BMD method to the relationship between renal effect markers and urinary Cd as an index of internal body burden [7,8,9,10,11]. The statistical validity and efficiency of the BMD and BMDL values were greater using the hybrid approach compared with methods involving categorization of continuous exposure and effect markers By using this hybrid approach, the BMDL of urinary Cd for renal effect markers in the Japanese [15,16,17,18] and Swedish population have been estimated [19]. The relationship between urinary Cd and renal dysfunction has not been evaluated in the Thai population

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