Comparative Study of Conocarpus erectus and Phoenix dactylifera as Plant Biomonitors of Particulate Matter Pollution in Kuwait over Three Land Use Classes

Magnetic plant biomonitoring has been proven to be an effective tool in the assessment of air quality. Kuwait presents a unique environment due to its dry desert climatic conditions and prevailing dry deposition patterns that may affect accumulation rates of magnetic mineral particles. This study evaluated two widely distributed ornamental species, buttonwood (Conocarpus erectus) and palm (Phoenix dactylifera) for their effectiveness as biomagnetic monitors over three different land use classes (urban, suburban and industrial land classes). The differences between land use classes were classified by their proximity to major pollution sources as well as population density. Leaf sampling was conducted over various heights and distances from the nearest road. Total leaf saturated isothermal magnetization (SIRM), hard isothermal magnetization (HIRM), hard isothermal magnetization percentage (HIRM%) and s-ratio have been measured. Scanning electron microscopy (SEM) was used to analyze leaf surface micromorphology. It was determined that NRM values are similar for all land use classes and species, ranging from 0.3 to 0.5 μA. Palm leaf overall magnetic concentration was identified to be higher at the industrial land use class than at the urban land use class, indicating high coercivity minerals to magnetically dominate the land use classes. Additionally, total leaf SIRM was determined to be higher at short distances of 0 - 5 meters from the vicinity of the road. The surface rugosity of palm has deep ridges and furrows with ununiform wax projections across the leaf surface, while buttonwood has a smooth wax film with low relief. Differences in leaf micromorphology in addition to plant physiology, justify species magnetic parametric variances. Palm leaf had an average SIRM value that is 120% higher than buttonwood. It has been highlighted that through the application of the magnetic parameter results to spatial distribution maps that there is an association between particulate matter (PM) and the locality of main roads and local services that may experience higher intensities of traffic.

Delonix regia and Casuarina equisetifolia as passive biomonitors and as bioaccumulators of atmospheric trace metals

The suitability of two common and ubiquitously distributed and exotic ornamental plant species in Nigeria-Delonix regia and Casuarina equisetifolia as biomonitors and as effective bioaccumulators of atmospheric trace metals （Cd, Pb, Zn and Cu） has been evaluated. Bark and leaf samples from these plant species were collected in June and July 2006 at five locations in Benin City. Four of the sampling sites were in areas of high traffic density and commercial activities, the fifth site is a remote site, selected to act as a control and also to provide background information for the metals. The plant samples were collected and processed using standard procedures and trace metals were determined using atomic absorption spectrometer. The bark of the plants was able to bioaccumulate the trace metals, especially Pb which originates from anthropogenic contributions in the city. The Pb range of 20.00-70.00 μg/g measured for the bark samples ofD. regia, exceeded the normal plant Pb concentration of 0.2-20.0 μg/g and most Pb data available in literature. The bark of the plants was observed to accumulate more metals compared to the leave, while D. regia was found to be slightly better than C. equisetifolia in trace metal uptake efficiency. Spatial variations in the distributions of Pb and Zn were significant （p 〈 0.05）, and the continuous use of leaded fuel in Nigeria was identified as the predominant source of Pb in the atmosphere.

Effect of Cadmium on the Developmental Instability of Anabas testudineus through Evaluation of Fluctuating Asymmetry of Eye Diameter

Biomonitoring using fish has been a popular method of assessing the toxic effects of cadmium concentrations of cadmium in water bodies and has led to bioaccumulation in fish contributing to various morphological alterations. Among the known effects of these alterations is developmental instability via fluctuating asymmetry (FA). The utilization of FA data is a simple yet effective method to evaluate the toxic effects of cadmium on the stability of development. This study used climbing perch (Anabas testudieneus) to assess the FA in the diameter of the eye because of low-level cadmium exposure. The left and right sides of the traits were measured once every four weeks for 16 weeks. The average measurements from both sides of the traits were used to calculate the FA value. Results found that the highest mean FA for the diameter of the eye was obtained in the highest treatment group, 0.015 mg/L. The results also indicate that increasing concentrations of cadmium exposure had a statistically significant effect on the FA of eye diameter. There was also a statistically significant interaction between the duration of exposure and treatment groups in FA of the diameter of the eye. The results from the study indicate that prolonged exposure to sub-lethal concentrations of cadmium can cause significant effects on the normal development of eyes in Anabas testudineus. This study can add to the body of research regarding fluctuating asymmetry as a tool to study developmental toxicants and assess other bilateral organs.

Sensitivity of Lichens to Diesel Exhaust under Laboratory Conditions

Lichen vegetation reacts very sensitively to a variety of air pollutants including increased nitrogen concentrations as well as to traffic exhaust in general, which makes lichens reliable monitoring organisms for atmospheric pollution. Recent environmental studies have shown that decreasing abundance of acidophytic lichen species and the increase of nitrophytic lichens can be explained by elevated levels of atmospheric nitric-compounds adsorbed onto nanoparticles. One major source of these atmospheric compounds amongst a wider pollution inventory is diesel exhaust—a mixture of gases and particle matter. This study aimed to shed light on the impact of diesel exhaust on the viability of six differently sensitive lichen species. Diesel exhaust particle concentrations in the laboratory experiments resembled those at a local highway during rush hour. By incubation in a closed stainless steel chamber we could exclude influences from other pollutants than diesel exhaust providing explicit data about the effects of diesel exhaust on lichens. The investigations revealed effects on the photosynthesis of the lichen photobionts and hence the lichen vitality. The conclusions of this study are that 1) the photobiont is affected stronger as the mycobiont and 2) older parts of the lichen are damaged first. Another remarkable result of this study is that 3) these lichens are regenerating to some extent during incubation-free periods—unless the organism is not damaged too much to restore photosynthetic activity. To our knowledge this is the first study evaluating the impact of diesel exhaust on lichens under laboratory conditions separate from other interfering pollutants.

Use of Atomic Absorption Spectrometry in Assessment of Biomonitor Plants for Lead,Cadmium and Copper Pollution

Eleven plant species were collected from the vicinity of lead-battery plant in the city of Gaziantep,Turkey.Lead,cadmium and copper concentrations in the soil and leaves of plants were determined by atomic absorption spectrometry.Lead,Cd and Cu concentrations in the soil samples taken from battery area were found to be in the ranges of 304～602,0.4～0.44 and 31～37 mg·kg-1,respectively.Significantly increased lead concentration up to 2 750 mg·kg-1 was found in the leaves of Eleagnus angustifolia L.plant.The lead concentrations in the other plant leaves taken from 50 m around battery factory followed the order Ailanthus altissima>Morus sp.>Juglans regia L.>Ficus carica L.>Cydonia oblonga Miller>Prunus x domestica L.The plants,Populus nigra L.,Eleagnus angustifolia L.and Salix sp.were found useful for Cd,and the plant,Eleagnus angustifolia L.for Pb,to be considered as potential biomonitor.Especially,leaves of trees and plants taken from the distance of 50 m from battery plant have relatively higher Pb concentrations.Therefore,people who and animals which live in this area and benefit from these soil and plants have vital risks.

Differences in the behavior characteristics between Daphnia magna and Japanese madaka in an on-line biomonitoring system

It is important to select suitable organisms to adapt the requirement of different environment monitoring purposes.Following our previous study,the behavioral responses of Daphnia magna and Japanese madaka （Oryzias latipes） were investigated and compared under flow-through conditions in an on-line biomonitoring system.The results showed that both D.magna and Japanese madaka had similar biological clock,but the circadian rhythms of Japanese madaka was more clearly recorded than that of D.magna.And the sensitivity of D.magna was about two orders of magnitudes higher than that of Japanese madaka in different types of toxic chemicals （dichlorovos,deltamethrin and cadmium chloride）.However,when both animals were used in an on-line biomonitoring system,the life span of D.magna was less than 7 days and Japanese madaka could last for more than one month without feeding.Therefore,D.magna was proposed to be a more sensitive bioindicator and was suitable for short term monitoring the pollution events at concentration level closing to the water quality standard,while Japanese madaka was more suitable for the long-term monitoring for accidental discharges.

Human biological monitoring of suspected .ndocrine-disrupting compounds

Endocrine-disrupting compounds are exogenous agents that interfere with the natural hormones of the body. Human biological monitoring is a powerful method for monitoring exposure to endocrine disrupting compounds. In this review, we describe human biological monitoring systems for different groups of endocrine disrupting compounds, polychiorinated biphenyls, brominated flame retardants, phthalates, alkylphenols, pesticides, metals, perfluronated compounds, parabens, ultraviolet filters, and organic solvents. The aspects discussed are origin to exposure, metabolism, matrices to analyse, analytical determination methods, determinants, and time trends.

Restoration processes of pollution zones in Hanjiang River

Two pollution zones in middle and lower reaches of Hanjiang River were selected for studying restoration processes. In each zones 6 stations were set up in upper stream of sewage outfall, 50m, 100 or 150m, 250 or 525m and 1250 or 3500m apart from the outfall. Chemical monitoring and microbial community biomonitoring were carried out simultaneously. Either the chemical monitoring or the biological monitoring proved the self-purification process of water body along with the increased distance from the sewage outfall. 4 biological parameters (species number of protozoa, percentage of phytomastigophora, diversity index and heterotrophy index) and parameter Seq of the colonization process all have statistically significant correlations with chemical comprehensive pollution indexes Pa and Pb.

An Estimation of the Daily Intake of Di(2-ethlhexyl) Phthalate(DEHP) among Workers in Flavoring Factories

Objective To estimate the daily intake of DEHP among workers in flavoring factories. Methods 71 workers in two flavoring manufacturers, 27 administrators in those factories and 31 laboratory technicians in a research institute were recruited and assigned to exposure group, control group 1 and control group 2 respectively. Their urinary DEHP metabolites, mono（2-ethylhexyl） phthalate （MEHP）, mono-（2-ethyl-5-hydroxyhexyl） phthalate （MEHHP）, mono-（2-ethyl-5-oxohexyl） phthalate （MEOHP）, were detected by isotope dilution-ultra performance liquid chromatography-tandem mass spectrometry（UPLC-MS/MS）. The urinary metabolites concentrations were converted into DEHP intake levels using two pharmacokinetic models： the urine creatinine-excretion （UCE） one and the urine volume （UV） one. Results No significant differences were found among the three groups. Based on the urinary concentrations of Z3MEHP, we got a median daily DEHP intake of 3.22 or 1.85 μg/kg body-weight/day applying the UV or UCE models respectively. Depending on the UV model, three subjects （2.34%） exceeded the RfD value given by US EPA and the P50 of estimate daily DEHP intakes accounted for 16.10% of the RfD value. No subjects exceeded the limitation depending on the UCE model. Conclusion The workers in flavoring factories were not supposed to be the high DEHP exposure ones and their exposure level remained at a low risk.

Benzene and lead exposure assessment among occupational bus drivers in Bangkok traffic

Four environmental and biological monitoring sites were strategically established to evaluate benzene and lead exposure assessment at various traffic zones of Bangkok Metropolitan Region(BMR). Biological measurement of 48 non air-conditioned, male bus drivers was carried to study the relationship between individual exposure levels and exposure biomarkers. The study group was further sub-divided into four age groups(16—25, 26—35, 36—45 and 46—55 years old) to monitor the age—related exposure effects. A total of 12 unexposed persons were deliberately chosen as the control group. Measurement of unmetobolized benzene in blood and analysis of urinary tt-Muconic acid urine and urinary creatinine are recommended as biomarkers of benzene exposure. Measurement of lead in blood and urine is also recommended for the biological monitoring of lead exposure. During the monitoring period, benzene and lead levels at Yaowarat Road was C_6H_6: 42.46±3.88 μg/m 3, Pb: 0.29±0.03 μg/m 3 and decreased to C_6H_6: 33.5±1.35 μg/m 3, Pb: 0.13±0.01 μg/m 3 at Phahonyothin Road. Significant difference was established between the nonsmoking exposed group and nonsmoking control group for blood benzene concentrations ( P <0.001, two-tailed, Mann-Whiteney U test). Strong correlations were also found between trans-trans-Muconic acid concentrations in post shift samples and atmospheric benzene concentrations. Similarly, good correlation between all of biomarkers and lead level in air is established from automobile emissions.The analysis revealed that among the occupational population in the urban sites, the driver groups were found to have the highest risk of benzene and lead exposures derived from automobile emission.

Advances of studies on biomonitoring of water pollution in China

The progress of biomonitoring on water pollution in recent years in China has been summarized in this paper.

Succession of aquatic microbial communities as a result of the water quality variations in continuous water

The changes of structural and functional parameters of aquatic microbial communities in continuous water on campus of Tsinghua University, China are investigated by polyurethane foam unit(PFU) method. The measured compositions of the communities include alga, protozoa, and some metazoa(such as rotifers). The measured indicators of water quality include water temperature, pH value, dissolved oxygen(DO), potassium permanganate index(COD Mn ), total nitrogen(TN), total phosphorus(TP) and chlorophyll-a(Chla). The trophic level, expressed by the trophic level indices(TLIc), is assessed with analytic hierarchy process and principal component analysis(AHP-PCA) method. The changing trends of the structural and functional parameters of aquatic microbial communities, such as Margalef index of diversity(D), Shannon-weaver index of diversity (H), Heterotropy index(HI), number of species when the colonization gets equilibrium(S eq ), colonizing speed constant(G) and time spent when 90 percent of S eq colonized in PFU(T 90% ), are also analyzed. The experimental results showed the succession of aquatic microbial communities along the water flow is consistent with the water quality changes, so the parameters of microbial community can reflect the changes of water quality from the ecological view.

Effects of heavy metal(Pb) concentration on some growth parameters of plants grown in lead polluted soil under organic fertilizer amendment

This study investigated morphological variation and biomass accumulation that occurred in Sida acuta and Chromolaena odorata plants grown in lead polluted soil under organic fertilizer amendment. The study was carried out in the screen house at the Biological Gardens of the Obafemi Awolowo University, Ile-Ife, Osun State. The experiment was a factorial combination of one heavy metal （Pb） at five levels of concentration （0, 200, 400, 800 and 1,000 mg/kg） in a completely randomized design, and were replicated three times for each of the two plants and two levels （0 g/kg and 9.4 g/kg） of organic fertilizer （OBD-Plus）. Each pot was filled with 5 kg of air-dried and sieved soil and placed on a plastic tray for the collection of excess water. Two weeks after planting, seedlings of uniform height were transplanted from the nursery to experimental pots at the rate of one seedling per pot and grown for 10 weeks. The growth parameters of the plants were biomonitored for 7 weeks. After 10 weeks of treatment, the plants were harvested and dried to calculate the biomass accumulation. The two plant species performed better under fertilizer application than without it. For each of the plant species the growth parameters decreased as the levels of Pb concentration increased. Furthermore, the plants＇ biomass decreased significantly （p 〈0.05） as the levels of Pb concentration increased. The organic fertilizer helped to improve the plants＇ performance in lead-polluted soil.

Incidents with Dioxins and PCBs in Food and Feed-Investigative Work, Risk Management and Economic Consequences

The identification of contamination sources within the food chain with polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzo-furans (PCDFs), (“dioxins”), and PCBs is difficult and complex. PCDD/PCDF can be formed as unintentional compounds in a number of chemical processes as well as in almost every combustion process. PCBs were intentionally produced chemicals that were manufactured for decades before the ban in marketing and use in many countries around 1985. The pattern of occurrence can change from the original source in particular via feedingstuffs to food of animal origin as result of bioaccumulation. A number of examples illustrate the challenging detective work and key scientific aspects for identification of the sources, for support of the risk management and for performance of monitoring programs. The contamination of milk and milk products in European countries with dioxins was caused by compound feeds containing citrus pulp pellets from Brazil which had high dioxin levels as a result of the use of heavily contaminated lime used for neutralization. The Belgian dioxin crisis was caused by a feed additive heavily contaminated with PCBs which were discharged into a recycled fat used in the production of animal feed. Guar gum from India was contaminated with sodium pentachlorophenate and dioxins. Clay was found to be possibly highly contaminated with dioxins possibly formed by geothermal processes over time;use of such clay as feed additive or for human intake led to elevated dioxin levels in food and humans. Bioanalytical screening in combination with comprehensive physicochemical investigations led to the detection of brominated flame retardants and brominated dioxins in a feed additive. Buffalo milk was contaminated in Italy presumably caused by illegal deposition of waste. High PCB levels in fuel oil for drying of breadcrumb used as a feed ingredient caused a major dioxin crisis with pork meat in Ireland. Fatty acids for technical purposes originating from a biodiesel company were used for production of feed fat which contaminated parts of the food chain in Germany. In addition to effects on human and animal health these incidents also have serious economic consequences which could be mitigated by more frequent control on food and feed. Addressing both these issues, the European Community has developed a strategy to reduce the presence of dioxins and PCBs in the environment and in feed and food comprising the establishment of maximum and action levels.

Estimation of Reference Values for PFOS and PFOA in Human Biomonitoring and Relevance of Exposure among Family Members in China

The reference values of serum perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) concentrations were evaluated based on the human blood samples collected from Kashi, Xinjiang. And human serum samples of family members from Liaoning were evaluated for levels of PFOS and PFOA with the purpose to compare exposure pathways for family members. Among the 110 blood specimens from Kashi, the detection frequency of PFOS and PFOA was 93% and 6%, respectively. Reference values of serum PFOS, evaluated as the 90th percentiles of the concentrations, were determined to be 6.44 μg/L. Significant positive correlations were observed for serum levels of PFOS and PFOA among family members in Liaoning. Specially, stronger correlation between mother and offspring was observed than that between father and offspring. And stronger correlation of serum PFOS and PFOA levels was observed among fam- ily members in rural areas than those in big and small-medium cities. Difference in the association of serum PFOS and PFOA level among family members suggested that exposure in the outdoor and working environment of different oc- cupations should be evaluated. Present study provides reference values for exposure assessment in China and potential pathways of human exposure to PFOS and PFOA.

Assessment of the Potential of Honeybees (<i>Apis mellifera</i>L.) in Biomonitoring of Air Pollution by Cadmium, Lead and Vanadium

The aim of our study was to explore whether honeybees (Apis mellifera L.) could be used as a reliable alternative to the standard mechanical devices for monitoring of air quality, in particular with respect to the concentration of the heavy metals cadmium (Cd), lead (Pb) and vanadium (V). We therefore tested whether the concentrations of these metals in adult honeybees and in ambient air were positively correlated, and whether differences in concentration between locations were similar for bees and air. On the basis of our measurements, conducted over a two-month period at three distinct locations in the Netherlands with each three replicate honeybee colonies placed next to mechanical monitoring devices, we concluded that a significant positive relationship between the concentrations in bees and in air could only be established for V. Also, only in the case of V, the differences between the three locations in mean concentration were similar for bees and air. Both outcomes were probably due to the relatively large range over which the concentrations of V varied, both in bees and in air, as compared to Cd and Pb. However, for V, as well as for Cd and Pb, the concentrations in ambient air were about two orders of magnitude below the established air quality standards. We therefore conclude that in the Netherlands, both variation and levels of the atmospheric concentrations of these metals are too low to establish a relationship between the concentration in bees and in air that is useful to present honeybees as an alternative to mechanical devices in monitoring of air pollution. However, in countries with larger variation and higher levels of the atmospheric concentrations of these metals, further exploration of the potential of honeybees in biomonitoring of air pollution may be worthwhile.

Use of Flame Atomic Absorption Spectroscopy and Multivariate Analysis for the Determination of Trace Elements in Human Scalp

The analysis of trace elements in human hair for use as biomarkers continues to generate considerable interest in environmental and bioanalytical studies, medical diagnostics, and forensic science. This study investigated the concentrations of essential and toxic elements (Fe, Mg, Ca, Cu, Zn, Cr, Cd, and Pb) using flame atomic absorption spectroscopy (FAAS) in human scalp hair obtained from subjects living in Forsyth County, North Carolina, USA. The influence of age, sex, race, and smoking habits on the levels of trace elements in the hair samples were also investigated. Additionally, analyses were subjected to a statistical, regression, and principal component analysis to evaluate inter-elemental association and possible pattern recognition in hair samples. Furthermore, Ca/Mg and Zn/Cu ratios, which are often used to evaluate the degree of Ca and Cu utilization in humans and as markers for various health related issues including, atherosclerosis, hypertension, insulin sensitivity, and pancreatic cancer, were calculated. The overall mean concentrations of Fe (25 μg/g), Ca (710 μg/g), Mg (120 μg/g), Zn (190 μg/g), Cu (12 μg/g), and Cr (0.20 μg/g) were found in hair samples. The trace element concentrations varied widely in hair samples as demonstrated by large range of concentrations obtained for each element. However, levels of Cd and Pb elements of <0.030 μg/g were detected in hair sample. In general, the levels of the trace elements in hair samples were poorly correlated. However, significant correlations were found between Ca and Mg (r = 0.840, p = 0.05). The levels of Fe, Ca, Mg, Zn, Cu, and Cr in hair samples and the calculated Ca/Mg and Zn/Cu ratios were found to be largely correlated with age, race, sex, and smoking habits.

Seasonal Changes in Copper and Cobalt Concentrations of PinusnigraL.,Cedrus libani and Cupressus arizonica Leaves to Monitor the Effects of Pollution in Elazig (Turkey)

The aim of this study is to examine seasonal changes in Cu and Co concentrations of three plant species for monitoring the effects of pollution in Elazig,Turkey.For this purpose,the leaves of the Pinus nigra L.,Cedrus libani and Cupressus arizonica together with soil samples were collected from different points depending on traffic intensity,nearness the city center and cement factory as well as control location during different months of the year.Flame atomic absorption spectrophotometer(FAAS) was used for measurement of the metals in clear digests after the dry ashing method.Copper and Co concentrations were in the ranges from 1.3to 2.6mg.kg-1 and<LOD to 0.26mg.kg-1 for Pinus nigra L.,1.2to 4.7mg.kg-1 and<LOD to 0.41mg.kg-1 for Cedrus libani and 1.5to 4.8mg.kg-1 and<LOD to 0.42mg.kg-1 for Cupressus arizonica,respectively.The levels observed for Cu and Co in the soil ranged from 12to 38mg.kg-1 and 6.0to 17mg.kg-1,respectively.

Index of Atmospheric Purity reflects the ecological conditions better than the environmental pollution in the Carpathian forests

The Index of Atmospheric Purity(IAP)is a popular tool used for the assessment of air quality in polluted urban areas,on the basis of phytosociological data of epiphytic lichen communities.We hypothesized that this indicator could also be used in less polluted forest areas to determine the quality of ecological conditions for lichens.The aim of the present study was to verify the use of IAP method in the assessment of environmental pollution,and alternatively for the assessment of general ecological conditions in protected mountain forests of Gorce National Park(Polish Western Carpathians)based on the epiphytic lichen biota associated with Picea abies.The spatial distribution of IAP values on monitored sites in GNP was compared with:1)spatial distribution of accumulated sulfur,nitrogen,selected heavy metals,and total heavy metals in Hypogymnia physodes thalli in 1993 and 2018(30 sites),2)mean ecological indicator values characterizing species requirements for light(L),substrate reaction(R)and nutrients(N),in 1993,2013 and 2018(33 sites).Generalized linear model and redundancy analysis were performed for disclosing most influencing factors affecting lichen communities.The study revealed a few negligible relationships between IAP values and accumulation of such elements as Ni,Mn,Cd,and Cr in both monitoring periods.Simultaneously,IAP can be useful for the identification of forest areas with a high degree of naturalness.

Urinary Creatinine Concentrations and Its Explanatory Variables in General Chinese Population:Implications for Creatinine Limits and Creatinine Adjustment

Objective The study aimed to analyze the applicability of the World Health Organization’s exclusionary guidelines for Urinary creatinine(Ucr)in the general Chinese population,and to identify Ucr related factors.Methods We conduct a cross-sectional study using baseline data from 21,167 participants in the China National Human Biomonitoring Program.Mixed linear models and restricted cubic splines(RCS)were used to analyze the associations between explanatory variables and Ucr concentration.Results The geometric mean and median concentrations of Ucr in the general Chinese population were 0.90 g/L and 1.01 g/L,respectively.And 9.36%samples were outside 0.3-3.0 g/L,including 7.83%below the lower limit and 1.53%above the upper limit.Middle age,male,obesity,smoking,higher frequency of red meat consumption and chronic kidney disease were associated significantly with higher concentrations of Ucr.Results of the RCS showed Ucr was positively and linearly associated with body mass index,inversely and linearly associated with systolic blood pressure,diastolic blood pressure,triglycerides level,and glomerular filtration rate,and were non-linearly associated with triiodothyronine.Conclusion The age-and gender-specific cut-off values of Ucr that determine the validity of urine samples in the general Chinese population were recommended.To avoid introducing bias into epidemiologic associations,the potential predictors of Ucr observed in the current study should be considered when using Ucr to adjust for variations in urine dilution.