Arsenic Intake Research Articles

Acute arsenic self-poisoning for suicidal purpose in a dentist: a case report

Arsenic is a classical poison that has been historically used since ancient times for homicidal purposes. More recently, episodes of deliberate or unintentional arsenic self-poisoning have been increasingly reported. We describe here a case of a 77-year old male patient with a history of major depression, who attempted suicide by ingestion of 4 g of arsenic trioxide. The man, a dentist by profession, used arsenic preparations for pulp devitalization. The patient was admitted to our hospital 5 h after arsenic ingestion with nausea and vomiting. Plain radiograph of the abdomen showed radio-opaque material in the stomach and small intestine. Nasogastric lavage, activated charcoal, and chelators were used to remove arsenic. On day 3, endoscopy disclosed the presence of gastritis and superficial ulcers. The patient developed significant anemia (Hb: 8.7 g/dL on day 7) without significant signs of hemolysis. He gradually recovered from anemia within 5 months. The patient did not suffer any adverse outcome in spite of having ingesting 4 g of arsenic, approximately 20 times the lethal dose.

DETERMINATION OF MERCURY AND ARSENIC CONTENT IN A FEW INDIAN AYURVEDIC MEDICINES BY MEANS OF ENERGY DISPERSIVE X-RAY FLUORESCENCE (EDXRF)

Elemental concentrations in some herbal medical products, produced by different ayurvedic pharmacies in India, were determined using Energy Dispersive X-Ray Fluorescence Spectrometry (EDXRF). All the eight products, which were studied, contained mercury, and four out of the eight products contained arsenic in varied amounts. Daily mercury and arsenic intakes by the patients taking these products, determined from the doses prescribed by the manufacturers, exceeded the recommendations by WHO. The present work does not argue on the toxicity of heavy metals in drugs but gives information about the presence of heavy metals at levels more than the required recommendations by various health regulatory bodies. This level of As and Hg calls for caution as far as their safe intake is concerned.

Evaluation of dietary status with respect to trace element intake from dry fruits consumed in Pakistan: a study using instrumental neutron activation analysis

Instrumental neutron activation analysis has been utilized for the quantification of 24 major, minor and trace elements in dried apricots (Prunus armeniaca), dates (Phoenix dectylifera), figs (Ficus carica) and raisins (Vitis vinifera) using a low-power reactor as the neutron source. The weekly intakes of aluminium, arsenic, boron, calcium, chlorine, cobalt, chromium, iron, mercury, potassium, sodium, magnesium, manganese, molybdenum, antimony, selenium and zinc have been calculated and compared with the Recommended Dietary Allowance/Estimated Safe and Adequate Dietary Intake values through consumption of 100 g dried fruit. Fairly adequate levels of calcium, cobalt, iron, potassium and magnesium were determined in these dried fruits while the contribution of chlorine, chromium, molybdenum and sodium to the Recommended Dietary Allowance was found to be insignificant. Apricot is a nutritionally rich source of potassium, magnesium and cobalt, while chlorine and manganese contents were found to be highest in dates. Figs are an ample source of calcium, iron, magnesium and manganese, whereas raisins provide the highest intake of chromium, molybdenum and sodium. The toxic element contents of these dry fruits are considerably below the tolerance limits.

Arsenic speciation in Japanese rice drinks and condiments

Rice has been demonstrated to be one of the major contributors to inorganic arsenic (i-As) intake in humans. However, little is known about rice products as additional source of i-As exposure. In this study, misos, syrups and amazake (a fermented sweet rice drink) produced from rice, barley and millet were analysed for total arsenic (t-As) and a subset of samples were also analyzed for As speciation. Rice based products displayed a higher i-As content than those derived from barley and millet. Most of the t-As in the rice products studied was inorganic (63-83%), the remainder being dimethylarsinic acid. Those who regularly consume rice drinks and condiments, such as the Japanese population and those who follow health conscious diets based on the Japanese cuisine, could reach up to 23% of the World Health Organization's Provisional Tolerable Daily Intake of i-As, by only consuming these kinds of products. This study provides a wide appreciation of how i-As derived from rice based products enters the human diet and how this may be of concern to populations who are already exposed to high levels of i-As through consumption of foods such as rice and seaweed.

Effect of rice-cooking water to the daily arsenic intake in Bangladesh: results of field surveys and rice-cooking experiments

The effect of rice-cooking water to the daily arsenic intake of Bangladeshi people was investigated. At the first field survey, uncooked rice and cooked rice of 29 families were collected. Their arsenic concentrations were 0.22+/-0.11 and 0.26+/-0.15 mg/kg dry wt, respectively. In 15 families, arsenic concentration in rice increased after cooking. Good correlation (R(2)=0.89) was observed between arsenic in rice-cooking water and the difference of arsenic concentration in rice by cooking. In the second survey, we collected one-day duplicated food of 18 families. As a result, we estimated that six of 18 families likely used the arsenic contaminated water for cooking rice even they drank less arsenic-contaminated water for drinking purpose. We also conducted rice-cooking experiments in the laboratory, changing arsenic concentration in rice-cooking water. Clear linear relationships were obtained between the arsenic in rice-cooking water and the difference of arsenic concentration in rice by cooking. Factors that affect arsenic concentration in cooked rice are suggested as follows: (1) arsenic concentration in uncooked rice, (2) that in rice-cooking water, (3) difference in water content of rice before and after cooking, and (4) types of rice, especially, the difference between parboiled and non-parboiled rice.

Effect of cooking method and rice type on arsenic concentration in cooked rice and the estimation of arsenic dietary intake in a rural village in West Bengal, India

Arsenic (As) contamination of rice plants can result in high total As concentrations (t-As) in cooked rice, especially if As-contaminated water is used for cooking. This study examines two variables: (1) the cooking method (water volume and inclusion of a washing step); and (2) the rice type (atab and boiled). Cooking water and raw atab and boiled rice contained 40 μg As l−1 and 185 and 315 μg As kg−1, respectively. In general, all cooking methods increased t-As from the levels in raw rice; however, raw boiled rice decreased its t-As by 12.7% when cooked by the traditional method, but increased by 15.9% or 23.5% when cooked by the intermediate or contemporary methods, respectively. Based on the best possible scenario (the traditional cooking method leading to the lowest level of contamination, and the atab rice type with the lowest As content), t-As daily intake was estimated to be 328 μg, which was twice the tolerable daily intake of 150 μg.

Clinical manifestation and influential factors in patients with acute arsenic poisoning

To investigate the clinical characteristics of acute arsenic poisoning and its influential factors. Clinical data of 47 cases of arsenic poisoning were collected and analyzed. Two cases of observation, 40 cases of mild acute poisoning, and 5 severe acute poisoning were investigated in this group. Myocardial enzyme activity was correlated with age and urine arsenic concentrations. Myocardial enzyme, the liver ALT, total bilirubin (TBil) and indirect bilirubin (IBil) were negatively correlated with vomiting frequency, with statistical significance (P < 0.05). Urine arsenic concentration was correlated with vomiting frequency and amount of soup drunk, with statistically significant difference (P < 0.05). Despite no statistical significance in age and amount of soup drunk, the patients with more vomiting or diarrhea had less urine arsenic concentrations, cardiac enzymes and liver enzyme concentration. Acute arsenic poisoning can lead to multiple organ damage. The damage is relevant with amount of arsenic intake, vomiting, diarrhea and urinary frequency arsenic concentration. So early use of gastric lavage, vomiting, poison discharges, and adequate application of effective antidote (Na-DMPS) as soon as possible, symptomatic treatment and the reinforced monitoring, are the rescue key for patients with acute arsenic poisoning.

Abstract 3760: Atherogenic Affects Of Arsenic: Role Of Endoplasmic Reticulum Stress And Unfolded Protein Response

Arsenic is a global water contaminant and EPA has listed arsenic as a high priority hazardous substance in the United States. Epidemiological studies suggest that chronic arsenic ingestion increases cardiovascular disease in humans, particularly, carotid atherosclerosis. However, mechanisms of arsenic-induced atherogenesis are unknown. We examined the effect of arsenic exposure on early lesion formation in apoE-null mice maintained on water supplemented with (0, 1, 5 and 50 ppm; 3–16 weeks of age) sodium arsenite. Arsenic, did not affect plasma cholesterol but decreased the triglycerides by 18±4 % (P&lt;0.05). NMR analysis of the lipoproteins showed a significant decrease in the abundance of large VLDL particle (&gt;60 nm diameter). Despite a significant decrease in plasma triglyceride, atherosclerotic lesion formation was significantly increased (2– 4 fold; P&lt;0.05 for all doses) in the aortic sinus and the aortic arch of the arsenic-fed mice in a dose dependent manner. Immunohistochemical analysis showed significant increase in the accumulation of macrophages, expression of MCP-1 and unfolded protein response (UPR) dependent activating transcription factor (ATF)-4 and ATF3, in the lesions of arsenic (1ppm) exposed mice. In vitro , arsenic (5–25 μM), significantly increased the expression of ICAM-1, transmigration of differentiated monocytes and expression of the pro-inflammatory cytokine IL-8 in vascular endothelial cells (vEC). Arsenic, also increased the expression of ER-chaperones Grp 78, HERP and calnexin (2– 6 fold; P&lt;0.01). Examination of the effect of arsenic on UPR showed that arsenic, induced the splicing of IRE-1 dependent, bZIP transcription factor XBP-1(alarm phase) and increased the phosphorylation of eIF2α (PERK mediated adaptive phase) by 3 fold (P&lt;0.01) in vEC. Arsenic also induced the expression of the downstream effecter proteins of eIF2α-ATF3 (8 fold; P&lt;0.01) and pro-apoptotic protein CHOP (4 fold; P&lt;0.01) in vEC. Chemical chaperone, phenyl butyric acid (PBA), attenuated the arsenic-induced expression of ATF3 (&gt;90%; P&lt;0.001) and CHOP (&gt;90%; P&lt;0.001). These data suggest that ER-stress and UPR could exacerbate arsenic-induced vascular inflammation and promote atherogenesis.

Does Arsenic Exposure Increase the Risk for Prostate Cancer?

Arsenic has been well documented as the major risk factor for blackfoot disease (BFD), a unique peripheral vascular disease that was endemic to the southwestern coast of Taiwan, where residents consumed artesian well water containing high levels of arsenic for more than 50 yr. Chronic arsenic exposure was also reported to be associated with mortality attributed to prostate cancer in a dose-response relationship. A tap-water supply system was implemented in the early 1960s in the BFD-endemic areas in Taiwan. Artesian well water was no longer used for drinking and cooking after the mid-1970s. The objective of this study was to determine whether prostate cancer mortality decreased after the improvement of drinking-water supply system through elimination of arsenic ingestion from artesian well water. Standardized mortality ratios (SMRs) for prostate cancer were calculated for the BFD-endemic area for the years 1971–2006. Results showed that mortality attributed to prostate cancer declined gradually after the improvement of drinking-water supply system. Based on the reversibility criterion, the association between arsenic exposure and development of prostate cancer is likely to be causal.

Arsenic and other trace elements contamination in groundwater and a risk assessment study for the residents in the Kandal Province of Cambodia

Concentrations of arsenic and other trace elements in groundwater were examined at three villages (PT, POT and CHL) in the Kandal Province of Cambodia. Concentrations of arsenic in the groundwater ranged from 6.64 (in POT village) to 1543 μg/L (in PT village), with average and median concentrations of 552 and 353 μg/L, respectively. About 86% out of fifteen samples contained arsenic concentrations exceeding the WHO drinking water guidelines of 10 μg/L. Concentrations of arsenic (III) varied from 4 (in POT village) to 1334 μg/L (in PT village), with an average concentration of 470 μg/L. In addition, about 67%, 80% and 86% of the groundwater samples had higher concentrations for, respectively, barium, manganese and lead than the WHO drinking water guidelines. These results reveal that groundwater in Kandal Province is not only considerably contaminated with arsenic but also with barium, manganese and lead. A risk assessment study found that one sample (PT25) had a cumulative arsenic concentration (6758 mg) slightly higher than the threshold level (6750 mg) that could cause internal cancer in smelter workers with chronic exposure to arsenic from groundwater. High cumulative arsenic ingestion poses a health threat to the residents of Kandal Province.

Dietary Intake of Methionine, Cysteine, and Protein and Urinary Arsenic Excretion in Bangladesh

BackgroundIn Bangladesh, millions of people are exposed to arsenic in drinking water; arsenic is associated with increased risk of cancer. Once ingested, arsenic is metabolized via methylation and excreted in urine. Knowledge about nutritional factors affecting individual variation in methylation is limited.ObjectivesThe purpose of this study was to examine associations between intakes of protein, methionine, and cysteine total urinary arsenic in a large population-based sample.MethodsThe study subjects were 10,402 disease-free residents of Araihazar, Bangladesh, who participated in the Health Effects of Arsenic Longitudinal Study (HEALS). Food intakes were assessed using a validated food frequency questionnaire developed for the study population. Nutrient composition was determined by using the U.S. Department of Agriculture National Nutrient Database for Standard Reference. Generalized estimating equations were used to examine association between total urinary arsenic across quintiles of nutrient intakes while controlling for arsenic exposure from drinking water and other predictors of urinary arsenic.ResultsGreater intakes of protein, methionine, and cysteine were associated with 10–15% greater total urinary arsenic excretion, after controlling for total energy intake, body weight, sex, age, tobacco use, and intake of some other nutrients.ConclusionsGiven previously reported risks between lower rates of arsenic excretion and increased rates of cancer, these findings support the role of nutrition in preventing arsenic-related disease.

Inorganic Arsenic in Rice Bran and Its Products Are an Order of Magnitude Higher than in Bulk Grain

Rice is more elevated in arsenic than all other grain crops tested to date, with whole grain (brown) rice having higher arsenic levels than polished (white). It is reported here that rice bran, both commercially purchased and specifically milled for this study, have levels of inorganic arsenic, a nonthreshold, class 1 carcinogen, reaching concentrations of approximately 1 mg/kg dry weight, around 10-20 fold higher than concentrations found in bulk grain. Although pure rice bran is used as a health food supplement, perhaps of more concern is rice bran solubles, which are marketed as a superfood and as a supplement to malnourished children in international aid programs. Five rice bran solubles products were tested, sourced from the United States and Japan, and were found to have 0.61-1.9 mg/kg inorganic arsenic. Manufactures recommend approximately 20 g servings of the rice bran solubles per day, which equates to a 0.012-0.038 mg intake of inorganic arsenic. There are no maximum concentration levels (MCLs) set for arsenic or its species in food stuffs. EU and U.S. water regulations, set at 0.01 mg/L total or inorganic arsenic, respectively, are based on the assumption that 1 L of water per day is consumed, i.e., 0.01 mg of arsenic/ day. At the manufacturers recommended rice bran solubles consumption rate, inorganic arsenic intake exceeds 0.01 mg/ day, remembering that rice bran solubles are targeted at malnourished children and that actual risk is based on mg kg(-1) day(-1) intake.

Arsenic-Induced Decreases in the Vascular Matrix

Chronic ingestion of arsenic is associated with increased incidence of respiratory and cardiovascular diseases. To investigate the role of arsenic in early events in vascular pathology, C57BL/6 mice ingested drinking water with or without 50 ppb sodium arsenite (AsIII) for four, five, or eight weeks. At five and eight weeks, RNA from the lungs of control and AsIII-exposed animals was processed for microarray. Sixty-five genes were significantly and differentially expressed. Differential expression of extracellular matrix (ECM) gene transcripts was particularly compelling, as 91% of genes in this category, including elastin and collagen, were significantly decreased. In additional experiments, real-time RT-PCR showed an AsIII-induced decrease in many of these ECM gene transcripts in the heart and NIH3T3 fibroblast cells. Histological stains for collagen and elastin show a distinct disruption in the ECM surrounding small arteries in the heart and lung of AsIII-exposed mice. Immunohistochemical detection of alpha-smooth muscle actin in blood vessel walls was decreased in the AsIII-exposed animals. These data reveal a functional link between AsIII exposure and disruption in the vascular ECM. These AsIII-induced early pathological events may predispose humans to respiratory and cardiovascular diseases linked to chronic low-dose AsIII exposure.

Transporters of arsenite in rice and their role in arsenic accumulation in rice grain.

Arsenic poisoning affects millions of people worldwide. Human arsenic intake from rice consumption can be substantial because rice is particularly efficient in assimilating arsenic from paddy soils, although the mechanism has not been elucidated. Here we report that two different types of transporters mediate transport of arsenite, the predominant form of arsenic in paddy soil, from the external medium to the xylem. Transporters belonging to the NIP subfamily of aquaporins in rice are permeable to arsenite but not to arsenate. Mutation in OsNIP2;1 (Lsi1, a silicon influx transporter) significantly decreases arsenite uptake. Furthermore, in the rice mutants defective in the silicon efflux transporter Lsi2, arsenite transport to the xylem and accumulation in shoots and grain decreased greatly. Mutation in Lsi2 had a much greater impact on arsenic accumulation in shoots and grain in field-grown rice than Lsi1. Arsenite transport in rice roots therefore shares the same highly efficient pathway as silicon, which explains why rice is efficient in arsenic accumulation. Our results provide insight into the uptake mechanism of arsenite in rice and strategies for reducing arsenic accumulation in grain for enhanced food safety.

Accumulation of arsenic in different fresh water fish species – potential contribution to high arsenic intakes

The aim of the study was to evaluate total arsenic (As) in five tissues (gills, mouthpiece, intestine, liver and muscles) of 10 fish species caught from As contaminated Manchar Lake (26°3′N: 67°6′E) Sindh Pakistan during 2006–2007. The total As concentration was determined by hydride generation atomic absorption spectrometry (HG-AAS), prior to microwave assisted acid digestion. The certified reference material DORM-2 (dogfish muscle) was used to check the quality control of the technique. The good agreement with the certified value at 95% confidence limit confirmed the validity of As determination method. The limit of detection (LOD) and limit of quantitation (LOQ) of As were 0.034 and 0.11 μg/g, respectively. The As concentration ranges in different tissues were obtained as: gills (1.01–10.4), mouth pieces (1.01–18.6), intestine (1.01–11.2), liver (3.51–10.9) and in muscles (2.12–15.2) μg/g on dried basis. The bioaccumulation factor (BAF) for As in fish muscles were found in two ranges (4.88–7.2) and (17.6–35.3). The contribution of the daily intake of As, based on the consumption of 250 g fresh fish muscles per day was found in the range of 0.1–0.76 μg, higher than WHO tolerable limit.

Impact of sedimentary arsenic through irrigated groundwater on soil, plant, crops and human continuum from Bengal delta: Special reference to raw and cooked rice

Existence of arsenic-rich (exceeds 2000 mg/kg) iron pyrite in Bengal delta sediments is responsible for arsenic release in aquifer. Ingestion of contaminated drinking water is not the only elevated source of arsenic to the diet. Irrigation of agricultural fields with arsenic-contaminated groundwater has led to arsenic build-up in soil, with subsequent elevation of arsenic in crops grown on these soils. About 50.7 and 11.2 kg of arsenic are withdrawn per year from 23 and 18 shallow tubewells, used for agricultural irrigation in the studied two districts Murshidabad and Nadia, respectively and deposited on lands throughout the year. Considerable higher amounts of arsenic are accumulated in paddy plants. Mean arsenic concentration in food categories is 107 μg/kg. Arsenic concentrations are high in cooked food and skin of the vegetables. Arsenic concentration in cooked rice increases with water arsenic concentration. About 70.2% of arsenic is recovered by using the analytical speciation extraction method. Inorganic arsenic and DMA contribute 89.5% and 10.5% of the total content of arsenic in food, respectively. About 0.081% and 1.57% of arsenic are accumulated in rice grain from arsenic-deposited lands and contaminated soils. The daily dietary intake of inorganic arsenic (μg/kg body wt./day) by an adult from rice grain itself (2.32) is higher than the WHO recommended PTDI value of inorganic arsenic (2.1) and inorganic arsenic contributes 96.8% of the total dietary intakes of arsenic. Population exposed to arsenic toxicity has been identified.

Decreased Urinary Beta-Defensin-1 Expression as a Biomarker of Response to Arsenic

Ingestion of arsenic (As) through contaminated drinking water results in increased risks of skin, lung, kidney, and bladder cancers. Due to its association with kidney and bladder cancers, we hypothesized that analysis of the urinary proteome could provide insight into the mechanisms of As toxicity. Urine from participants in a cross-sectional As biomarker study conducted in Nevada, classified as having either high (>or= 100 microg total urinary As/l) or low exposure (< 100 microg total urinary As/l) was analyzed by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry. Two polypeptides, 2.21 and 4.37 kDa, were significantly decreased in the high exposure group (p < 0.05) and were limited to men when stratified by sex. To replicate these findings, urine from participants in a second As study in Chile was analyzed and results confirmed the decrease of the 4.37 kDa polypeptide as well as a 4.76 kDa polypeptide among highly exposed men. These peaks were identified and confirmed as human beta-defensin-1 (HBD-1) peptides. In a separate in vitro experiment, gene expression analysis of As-treated cell lines demonstrated reduced HBD1 mRNA confirming that the observed decrease in HBD-1 resulted from As exposure. HBD-1 is an antimicrobial peptide constitutively expressed in multiple tissues including epithelial cells of the respiratory and urogenital systems. Recent studies support its role as a tumor suppressor gene for urological cancers suggesting that decreased HBD-1 levels may play a role in the development of cancers associated with As exposure. Further studies are warranted to investigate the role of HBD-1 in As-related toxicity.

Exposure to inorganic arsenic from rice: A global health issue?

Many Bangladeshi suffer from arsenic-related health concerns. Most mitigation activities focus on identifying contaminated wells and reducing the amount of arsenic ingested from well water. Food as a source of arsenic exposure has been recently documented. The objectives of this study were to measure the main types of arsenic in commonly consumed foods in Bangladesh and estimate the average daily intake (ADI) of arsenic from food and water. Total, organic and inorganic, arsenic were measured in drinking water and in cooked rice and vegetables from Bangladeshi households. The mean total arsenic level in 46 rice samples was 358 μg/kg (range: 46 to 1110 μg/kg dry weight) and 333 μg/kg (range: 19 to 2334 μg/kg dry weight) in 39 vegetable samples. Inorganic arsenic calculated as arsenite and arsenate made up 87% of the total arsenic measured in rice, and 96% of the total arsenic in vegetables. Total arsenic in water ranged from 200 to 500 μg/L. Using individual, self-reported data on daily consumption of rice and drinking water the total arsenic ADI was 1176 μg (range: 419 to 2053 μg), 14% attributable to inorganic arsenic in cooked rice. The ADI is a conservative estimate; vegetable arsenic was not included due to limitations in self-reported daily consumption amounts. Given the arsenic levels measured in food and water and consumption of these items, cooked rice and vegetables are a substantial exposure pathway for inorganic arsenic. Intervention strategies must consider all sources of dietary arsenic intake.

Is Colon Cancer Mortality Related to Arsenic Exposure?

Arsenic has been well documented as the major risk factor for blackfoot disease (BFD), a unique peripheral vascular disease that was endemic to the southwestern coast of Taiwan, where residents consumed high-arsenic artesian well water for more than 50 yr. Chronic arsenic exposure was also reported to be associated with increased mortality attributed to colon cancer. A tap-water supply system was implemented in the early 1960s in the BFD-endemic areas. Artesian well water was no longer used for drinking and cooking after the mid-1970s. The objective of this study was to determine whether colon cancer mortality decreased after the improvement of the drinking-water supply system through elimination of arsenic ingestion from artesian well water. Standardized mortality ratios (SMRs) for colon cancer were calculated for the BFD-endemic area for the years 1971–2006. Results showed that mortality due to colon cancer declined in males, but not in females, gradually after the improvement of drinking-water supply system. Based on the reversibility criterion, the association between arsenic exposure and colon cancer incidence is likely to be causal for males but not females. The possibility that our results may be due to chance should be considered; however, gender-specific differences in arsenic metabolism may be a critical factor.

Inorganic arsenic levels in baby rice are of concern

Inorganic arsenic is a chronic exposure carcinogen. Analysis of UK baby rice revealed a median inorganic arsenic content ( n = 17) of 0.11 mg/kg. By plotting inorganic arsenic against total arsenic, it was found that inorganic concentrations increased linearly up to 0.25 mg/kg total arsenic, then plateaued at 0.16 mg/kg at higher total arsenic concentrations. Inorganic arsenic intake by babies (4–12 months) was considered with respect to current dietary ingestion regulations. It was found that 35% of the baby rice samples analysed would be illegal for sale in China which has regulatory limit of 0.15 mg/kg inorganic arsenic. EU and US food regulations on arsenic are non-existent. When baby inorganic arsenic intake from rice was considered, median consumption (expressed as μg/kg/d) was higher than drinking water maximum exposures predicted for adults in these regions when water intake was expressed on a bodyweight basis.