Embryotoxic Thresholds of Mercury: Estimates from Individual Mallard Eggs

Eighty pairs of mallards (Anas platyrhynchos) were fed an uncontaminated diet until each female had laid 15 eggs. After each female had laid her 15th egg, the pair was randomly assigned to a control diet or diets containing 5, 10, or 20 μg/g mercury as methylmercury until she had laid a second set of 15 eggs. There were 20 pairs in each group. After the second set of 15 eggs, the pair was returned to an uncontaminated diet, and the female was permitted to lay another 30 eggs. For those pairs fed the mercury diets, the even-numbered eggs were incubated and the odd-numbered eggs were saved for possible mercury analysis. Mercury in the even-numbered eggs was estimated as the average of what was in the neighboring odd-numbered eggs. Neurological signs of methylmercury poisoning were observed in ducklings that hatched from eggs containing as little as 2.3 μg/g estimated mercury on a wet-weight basis, and deformities were seen in embryos from eggs containing about 1 μg/g estimated mercury. Although embryo mortality was seen in eggs estimated to contain as little as 0.74 μg/g mercury, there were considerable differences in the sensitivity of mallard embryos, especially from different parents, with some embryos surviving as much as 30 or more μg/g mercury in the egg. Received: 9 February 2002/Accepted: 12 June 2002     

Mercury accumulation in mallards fed methylmercury with or without added DDE

Adult female mallards (Anas platyrhynchos) were fed a control diet or diets containing 1 ppm methylmercury chloride, 5 ppm methylmercury chloride, 1 ppm methylmercury chloride plus 5 ppm DDE, or 5 ppm methylmercury chloride plus 5 ppm DDE. The presence of DDE in the diet did not affect retention of mercury in breast muscle or eggs. There was a good correlation between the levels of mercury in the breast muscle of females and their eggs, and this correlation was unaffected by the presence of DDE in the diet. This correlation suggests that one could predict mercury levels in female mallards in the field when only eggs have been collected and vice versa.     

Effects of methylmercury on approach and avoidance behavior of mallard ducklings

Summary Mallard ducks were fed a control diet or a diet containing 0.5 or 3 ppm mercury (as methylmercury dicyandiamide) based on the dry feed. These mercury diets are approximately equivalent to 0.1 and 0.6 ppm mercury in a natural succulent diet. I measured for the ducklings the approach behavior in response to a tape-recorded maternal call and the avoidance of a frightening stimulus.There were no significant differences among controls and ducklings from mercury-treated parents in the percentage of ducklings that approached the tape-recorded call. Control ducklings, however, moved back and forth toward the call more than ducklings from mercury-treated parents and also spent more time in the end of the runway near the loudspeaker than ducklings whose parents were fed a diet containing 0.5 ppm mercury.Compared to control ducklings, ducklings from parents fed a diet containing 0.5 or 3 ppm mercury were hyper-responsive in the test of avoidance of a frightening stimulus.Mallard eggs collected in the wild have been found to contain levels of mercury exceeding the 1 ppm (wet-weight) found in the eggs of hens fed a diet containing 0.5 ppm, but there are no reports of mallard eggs collected in the wild that were found to contain as much mercury (6 to 9 ppm) as eggs from hens fed a diet containing 3 ppm mercury. On a dry-weight basis, the concentration of mercury in the eggs was about 6 times as great as that in the feed for ducks fed the 0.5 ppm mercury diet and about 6 to 9 times as great for ducks fed the 3 ppm mercury diet.     

Effects of low dietary levels of methyl mercury on mallard reproduction

Summary Mallard ducks were fed a control diet or a diet containing 0.5 ppm or 3 ppm mercury (as methylmercury dicyandiamide). Health of adults and reproductive success were studied. The dietary level of 3 ppm mercury had harmful effects on reproduction, although it did not appear to affect the health of the adults during the 12 months of dosage. Ducks that were fed the diet containing 0.5 ppm mercury reproduced as well as controls, and ducklings from parents fed 0.5 ppm mercury grew faster in the first week of life than did controls.The greatest harm to reproduction associated with the diet containing 3 ppm mercury was an increase in duckling mortality, but reduced egg laying and increased embryonic mortality also occurred.During the peak of egg laying, eggs laid by controls tended to be heavier than eggs laid by ducks fed either level of mercury; however, there seemed to be no eggshell thinning associated with mercury treatment.Levels of mercury reached about 1 ppm in eggs from ducks fed a dietary dosage of 0.5 ppm mercury and between 6 and 9 ppm in the eggs from ducks fed 3 ppm mercury.     

Mercury residues in tissues of dead and surviving birds fed methylmercury.

Concentrations of mercury in passerine birds fed diets containing 40 ppm methylmercury were similar in tissues of birds that died from mercury poisoning and in those that were sacrificed after half the group had died. Residues were higher in tissues of birds that died, but the differences were not statistically significant. Residue levels were highest in livers, followed by kidneys and brains. Levels of mercury were similar in breast muscle, carcass, and whole body. Mercury levels were highest in redwinged blackbirds, lowest in grackles, and intermediate in starlings and cowbirds. Mercury concentrations exceeded 20 ppm in all tissues of all species and were similar to levels reported in wild birds known to have died of mercury poisoning.     

Mercury residues in tissues of dead and surviving birds fed methylmercury

Summary Concentrations of mercury in passerine birds fed diets containing 40 ppm methylmercury were similar in tissues of birds that died from mercury poisoning and in those that were sacrificed after half the group had died. Residues were higher in tissues of birds that died, but the differences were not statistically significant. Residue levels were highest in livers, followed by kidneys and brains. Levels of mercury were similar in breast muscle, carcass, and whole body. Mercury levels were highest in redwinged blackbirds, lowest in grackles, and intermediate in starlings and cowbirds. Mercury concentrations exceeded 20 ppm in all tissues of all species and were similar to levels reported in wild birds known to have died of mercury poisoning.     

DDT thins shells of eggs from mallard ducks maintained onad libitum or controlled-feeding regimens

Mallard ducks were fed diets containing various levels of technical DDT or chemically purep,p'-DDT, or dieldrin. Either technical DDT orp,p'-DDT at 20 ppm or greater, or dieldrin at 10 ppm caused a statistically significant reduction in eggshell thickness, weight, and calcium. Shells of eggs from ducks fed 40 ppm ofp,p'-DDT were about 20% thinner than those from control ducks, and shells of eggs from ducks fed 10 ppm of dieldrin were about 6% thinner than those from controls. The reduction in eggshell thickness was linear with increasing dose of DDT to 40 ppm, and with increasing dose of dieldrin through all levels studies. Eggshell thinning occurred regardless of whether the diets containing DDT were fed underad libitum or controlled conditions. DDT fed at 200 ppm was lethal to the ducks. Neither DDT nor dieldrin affected weight of the eggs or rate of egg production.Published with the approval of the Director of the North Dakota Agricultural Experiment Station as Journal Article No. 462.     

Dieldrin and p,p′—DDT effects on egg production and eggshell thickness of chickens

Summary Sixty Leghorn hens were randomly divided into 5 groups of 12 and individually fed a control diet, or diets containing 10 and 20 ppm dieldrin, or diets containing 100 and 200 ppm p,p-DDT for a 12-week period. Average egg production per bird, egg weight, dry shell weight, shell thickness (not including membranes), and shell calcium were not affected by feeding the insecticides. In addition, the length of the clutch or the number of clutches during the 12-week period were not affected. However, egg weight increased with time during the experiment, and eggshell thickness decreased with successive eggs within a clutch.Published with the approval of the director of the North Dakota Agricultural Experiment Station as Journal Article No. 301.     

Dietary Toxicity and Tissue Accumulation of Methylmercury in American Kestrels

American kestrels (Falco sparverius) were fed meat diets containing 0, 3, 6, or 12 ppm (dry weight) methylmercury chloride. Birds fed the 12-ppm diet started to show signs of neurotoxicity after 26 days and all died in 39–49 days. One male kestrel fed the 6-ppm diet died after 75 days of exposure and several others showed signs of neurotoxicity after 45 days. None of the birds fed the 3-ppm diet died or showed signs of toxicity. After 59 days of exposure, mercury concentrations in the liver, kidney, and blood of nonreproducing kestrels increased with increasing dietary concentration. Tissue concentrations of mercury also steadily increased over time in birds fed diets with 6 ppm mercury, which were necropsied at 8, 15, 29, or 59 days of exposure, reaching mean total mercury concentrations of 57, 46, and 45 ppm (wet weight) at 59 days in the liver, kidney, and whole blood, respectively. Two pairs of kestrels at each dietary concentration were allowed to breed. Eggs averaged 8.3 and 18.1 ppm (wet weight) total mercury from birds fed 3- and 6-ppm diets, respectively. Feathers grown during mercury exposure contained high concentrations of mercury: Birds fed 3- and 6-ppm diets contained 275 and 542 ppm total mercury, respectively.     

Effects of methylmercury on reproduction in American kestrels

Sixty breeding pairs of captive American kestrels (Falco sparverius) were exposed to a range of sublethal dietary concentrations of mercury (Hg), in the form of methylmercuric chloride, and their subsequent reproduction was measured. Egg production, incubation performance, and the number and percent of eggs hatched decreased markedly between 3.3 and 4.6 mg/kg dry weight of Hg (1.2 and 1.7 mg/kg wet wt), in the diet. The number of fledglings and the percent of nestlings fledged were reduced markedly at 0.7 mg/kg dry weight (0.3 mg/kg wet wt) and declined further between 2 and 3.3 mg/kg dry weight (0.7 and 1.2 mg/kg wet wt). Dietary concentrations of >or=4.6 mg/kg dry weight (1.7 mg/kg wet wt) were associated with total fledging failure. The estimated decline in fledged young per pair (24%, Bayesian regression) for kestrels consuming 0.7 mg/kg dry weight (0.3 mg/ kg wet wt) raises concerns about population maintenance in areas subject to high inputs of anthropogenic Hg. Mercury concentrations in 20 second-laid eggs collected from all groups were related to dietary concentrations of Hg, and the Hg concentrations in 19 of these eggs were related to eggs laid and young fledged. Concentrations of Hg in eggs from the highest diet group (5.9 mg/kg dry wt; 2.2 mg/kg wet wt) were higher than egg concentrations reported for either wild birds or for captive birds (nonraptors) fed dry commercial food containing 5 mg/kg methylmercury. Accumulation ratios of Hg from diets to eggs were higher than those reported for feeding studies with other species.     

Factors Affecting the Toxicity of Methylmercury Injected into Eggs

We developed a standardized protocol for comparing the sensitivities of the embryos of different bird species to methylmercury when methylmercury was injected into their eggs. During the course of developing this protocol, we investigated the effects of various factors on the toxicity of the injected methylmercury. Most of our experiments were done with chicken (Gallus domesticus), mallard (Anas platyrhynchos), and ring-necked pheasant (Phasianus colchicus) eggs, all of which were purchased in large numbers from game farms. A smaller amount of work was done with double-crested cormorant (Phalacrocorax auritus) eggs collected from the wild. Several solvents were tested, and corn oil at a rate of 1 μl/g egg contents was selected for the final standardized protocol because it had minimal toxicity to embryos and because methylmercury dissolved in corn oil yielded a dose–response curve in a range of egg concentrations that was similar to the range that causes reproductive impairment when the mother deposits methylmercury into her own eggs. The embryonic stage at which eggs were injected with corn oil altered mercury toxicity; at early stages, the corn oil itself was toxic. Therefore, in the final protocol we standardized the time of injection to occur when each species reached the morphologic equivalent of a 3-day-old chicken embryo. Although solvents can be injected directly into the albumen of an egg, high embryo mortality can occur in the solvent controls because of the formation of air bubbles in the albumen. Our final protocol used corn oil injections into the air cell, which are easier and safer than albumen injections. Most of the methylmercury, when dissolved in corn oil, injected into the air cell passes through the inner shell membrane and into the egg albumen. Most commercial incubators incubate eggs in trays with the air cell end of the egg pointing upward, but we discovered that mercury-induced mortality was too great when eggs were held in this orientation. In addition, some species of bird eggs require incubation on their sides with the eggs being rolled 180° for them to develop normally. Therefore, we adopted a procedure of incubating the eggs of all species on their sides and rolling them 180° every hour. Little has been published about the conditions of temperature, humidity, and the movements to which eggs of wild birds need to be subjected for them to hatch optimally under artificial incubation. Not unexpectedly, hatching success in an artificial incubator is generally less than what natural incubation by the parents can achieve. However, the survival of control embryos of most wild bird species was good (generally ≥ 80%) up to within 1 or 2 days of hatching when we incubated the eggs at 37.5°C (or 37.6°C for gallinaceous species) at a relative humidity that resulted in an approximate 15% to 16% loss in egg weight by the end of incubation and by incubating the eggs on their sides and rolling them 180°/h. To improve statistical comparisons, we used survival through 90% of incubation as our measurement to compare survival of controls with survival of eggs injected with graded concentrations of mercury.     

Reproductive Performance of Two Generations of Female Semidomesticated Mink Fed Diets Containing Organic Mercury Contaminated Freshwater Fish

Semidomesticated female mink (Mustela vison) were fed daily diets containing 0.1 ppm, 0.5 ppm, and 1.0 ppm of total mercury. Piscivorous and nonpiscivorous fish naturally contaminated with organic mercury were used to prepare the diets. Twenty-month-old females (G1 generation) that were exposed to the experimental diets for approximately 400 days in 1994 and 1995 and their 10-month-old female offspring (G2 generation) that were exposed to mercury for approximately 300 days in 1995, were all mated to 10-month-old males. Males were fed the diet containing 0.1 ppm mercury 60 days prior to the mating season. Diets containing 0.1 ppm and 0.5 ppm were not lethal to G1 and G2 females for an exposure period of up to 704 days. At the age of 11 months, mortalities occurred in 1994 for G1 females (30/50) and in 1995 for G2 females (6/7) fed the 1.0 ppm mercury diet after 90 days and 330 days of exposure, respectively. The length of the gestation periods and the number of kits born per female were not different among dietary groups for the two generations of females. The proportion of females giving birth was low for all groups, except for the G1 females fed the 0.1 ppm diet. There was an inverse relationship between whelping proportion and exposure group, but was not statistically significant. There was evidence that kits were exposed to mercury both in utero and/or during lactation as indicated by the presence of mercury in their livers. Mercury exposure did not influence the survival and growth of neonatal kits. Received: 11 November 1997/Accepted: 24 August 1998     

Dietary selenium protection of methylmercury intoxication of Japanese quail

Summary Selenium, as sodium selenite, added at 5 ppm to purified diets of Japanese quail protected against methylmercury intoxication. Selenium fed simultaneously with methylmercury to quail for 9 weeks gave complete protection. However, feeding selenium with methylmercury for 4 weeks, followed by a diet containing only methylmercury, delayed the onset of methylmercury intoxication for 1–2 weeks as compared to quail not pretreated with selenium. On diets which contained 20 ppm of methylmercury but no selenium, over 90% mortality was observed for young quail within 2 weeks, and mature quail within 4 weeks. Methylmercury residues in liver, kidney, and brain are higher in male than female quail. High methylmercury content of these organs, or in produced eggs, does not indicate that birds will show evidence of methylmercury toxicosis.Approved by the Director of the New York State Agricultural Experiment Station for publication as Journal Paper No. 2012.     

Influences of dietary protein levels and phytate contents on zinc requirement in rats

This study investigates whether the effects of increased dietary levels of soy protein on zinc-deficient rats are due to the dietary protein content. Rats were fed two levels of demineralized soy protein (DP) diets and two levels of egg albumin (EA) diets including 7 ppm zinc (Experiment 1). Growth was depressed in rats fed a 20% DP diet (0.43% phytate) but not in those fed a 10% EA diet containing 7 ppm zinc. Zinc concentrations in the serum, femur and kidney were lower in rats fed the 20% DP diet than those fed a 10% DP (0.20% phytate) diet, and they were also lower in rats fed the 10% EA diet than those fed a 5% EA diet. Zinc concentrations in the serum and femur of rats fed the 10% DP diet or the 20% DP diet were decreased compared with those fed the 5% EA diet or the 10% EA diet, respectively. Under zinc-deficient conditions (<0.4 ppm Zn), the survival time shortened (Experiment 2) and the zinc concentration in the serum and femur decreased faster (Experiment 3) in rats fed the 10% EA diet compared with those fed the 5% EA diet. The survival times and time courses of these parameters show that the zinc requirements of rats increased with the dietary protein level. The increased zinc requirement of rats that accompanied increasing dietary soy protein was due to the dietary protein content as well as the dietary phytate content.     

Influences of dietary protein levels and phytate contents on zinc requirement in rats

This study investigates whether the effects of increased dietary levels of soy protein on zinc-deficient rats are due to the dietary protein content. Rats were fed two levels of demineralized soy protein (DP) diets and two levels of egg albumin (EA) diets including 7 ppm zinc (Experiment 1). Growth was depressed in rats fed a 20% DP diet (0.43% phytate) but not in those fed a 10% EA diet containing 7 ppm zinc. Zinc concentrations in the serum, femur and kidney were lower in rats fed the 20% DP diet than those fed a 10% DP (0.20% phytate) diet, and they were also lower in rats fed the 10% EA diet than those fed a 5% EA diet. Zinc concentrations in the serum and femur of rats fed the 10% DP diet or the 20% DP diet were decreased compared with those fed the 5% EA diet or the 10% EA diet, respectively. Under zinc-deficient conditions (< 0.4 ppm Zn), the survival time shortened (Experiment 2) and the zinc concentration in the serum and femur decreased faster (Experiment 3) in rats fed the 10% EA diet compared with those fed the 5% EA diet. The survival times and time courses of these parameters show that the zinc requirements of rats increased with the dietary protein level. The increased zinc requirement of rats that accompanied increasing dietary soy protein was due to the dietary protein content as well as the dietary phytate content.     

Mercury concentrations in three species of fish from North Atlantic offshore waters

Mercury concentrations were determined in tissues and organs of spiny dogfish (Squalus acanthias), cusk (Brosme brosme), and blackbellied redfish (Helicolenus dactylopterus) collected from Atlantic Ocean waters off the northeastern coast of the United States. Information was obtained on the spatial and temporal distribution of mercury in the organs and tissues of these fish.Cusk were obtained from 2 locations and blackbellied redfish from 4 locations. The mercury levels in both muscle and liver of cusk averaged about 0.30 ppm for one and 0.16 ppm for the second location. Gills and kidneys of cusk had mercury levels that averaged 0.08 ppm for both collections. In blackbellied redfish mercury levels in muscle and liver averaged about 0.08 ppm for all locations; gill and kidney tissues of this fish were less than 0.2 ppm.Spiny dogfish were obtained from 5 areas. No significant difference in mercury levels was found in muscle tissue as related to geographic area. Mercury levels ranged from 0.21 to 0.62 ppm. The kidneys of dogfish contained about 54% of the mercury level of muscle. The mercury level in gills of dogfish ranged from 0.06 to 0.21 ppm.Spiny dogfish pups were obtained from 6 adult females. Samples of muscle, liver, gill, kidney, and yolk of pups were analyzed for mercury. These same samples, except for the yolk, were obtained from the adult females. Mercury levels in all pup samples were less than 0.03 ppm, while mercury levels in adult females ranged from 0.03 to 1.1 ppm in all tissues and organs.     

The effect of mirex on reproduction of Japanese quail and on characteristics of eggs from Japanese quail and chickens

Laying White Leghorn chickens were fed mirex at 0, 5, 10, 20, 40, 80, and 160 ppm for 12 weeks, and laying Japanese quail were fed mirex at 0, 5, 40, and 80 ppm for 12 weeks. The data suggest that dietary mirex at these levels did not affect egg production, egg weight, shell thickness, shell calcium, the proportion of broken eggs, or the proportion of soft-shelled eggs of either chickens or quail. Statistical significance (P < 0.05) associated with dietary mirex was detected in the analysis of eggshell weight for chickens; however, because a dose-response relationship of shell weightvs. level of mirex fed was not evident, this observation was attributed to chance. The data suggest that dietary mirex did not affect eggshell weight, fertility, or hatchability of quail. Mirex accumulation in eggs and carcasses of both species was proportional to dose and was slightly higher in quail than in chickens.     

Intestinal absorption and excretion of zinc in streptozotocin-diabetic rats as affected by dietary zinc and protein

65Zn was used to examine the effects of dietary zinc and protein on true zinc absorption and intestinal excretion of endogenous zinc by an isotope dilution technique in streptozotocin-diabetic and control rats. Four groups each of diabetic and control rats were fed diets containing 20 ppm Zn, 20% egg white protein (HMHP); 20 ppm Zn, 10% egg white protein (HMLP); 10 ppm Zn, 20% egg white protein (LMHP); and 10 ppm Zn, 10% egg white protein (LMLP). Measurement of zinc balance was begun 9 d after an i.m. injection of 65Zn. True zinc absorption and the contribution of endogenous zinc to fecal zinc excretion were calculated from the isotopically labeled and unlabeled zinc in the feces, duodenum and kidney. Results from the isotope dilution study indicated that diabetic rats, but not control rats, absorbed more zinc from 20 ppm zinc diets than from 10ppm zinc diets and that all rats absorbed more zinc from 20% protein diets than from 10% protein diets. Furthermore, all rats excreted more endogenous zinc from their intestines when dietary zinc and protein levels resulted in greater zinc absorption. In diabetic and control rats, consuming equivalent amounts of zinc, the amount of zinc absorbed was not significantly different, but the amount of zinc excreted by the intestine was less in the diabetic rats. Decreased intestinal excretion of endogenous zinc may be a homeostatic response to the increased urinary excretion of endogenous zinc in the diabetic rats and may also lead to the elevated zinc concentrations observed in some organs of the diabetic rats.     

Eggshell thinning in ring doves exposed top,p′-dicofol

Ring doves (Streptopelia risoria) were brought into breeding condition and, after laying two clutches of two eggs each, were fed one of three experimental diets containing either 33.4 ppm dicofol (1, 1-bis(p-chlorophenyl)-2,2,2-trichioroethanol), 37 ppmp,pi DDE (2,2-bis (p-chlorophenyl)-1,1 dichloroethylene), or no toxicant (control). Mean shell thicknesses of eggs produced on experimental diets were: control, 156 x; DDE, 145 ; and dicofol 142 . Birds fed DDE produced eggs with shells a mean 5.6% thinner than pre-treatment eggs, while birds fed dicofol produced eggs with shell means 7.2% thinner. No change in shell thickness was found in eggs from control doves. Analysis of covariance revealed a statistically significant effect of decreasing eggshell thickness over time in doves fed DDE and dicofol diets but not in control birds. Egg production was significantly lower in both dicofol-fed and DDE-fed birds when compared with controls. Control birds produced a mean of 1.97 eggs per clutch. Dicofol- and DDE-treated birds produced 1.88 and 1.79 eggs per clutch, respectively. The proportion of eggs found cracked or broken in the nest was greatest in birds fed dicofol, with 16.9% of all eggs broken or cracked, compared to 7.9% of eggs from the DDE group and 5.7% of eggs from control group. Selected eggs were analyzed for residues of dicofol, dichlorobenzophenone (DCBP), and DDE in the yolk. For the birds fed the dicofol diet, DDE residues in treatment eggs ranged from 0.036 to 0.119 ppm wet weight. DDE residues in pre-treatment eggs ranged from 0.013 to 0.080 ppm. Dicofol residues ranged from 2.62 ppm to 22.58 ppm. DCBP residues ranged from 2.55 to 17.68 ppm. Only residues of dicofol showed a significant correlation with percent shell thinning.     

Toxicity of methylmercury injected into eggs when dissolved in water versus corn oil

In a previous study, the embryotoxicity of methylmercury dissolved in corn oil was compared among 26 species of birds. Corn oil is not soluble in the water-based matrix that constitutes the albumen of an egg. To determine whether the use of corn oil limited the usefulness of this earlier study, a comparison was made of the embryotoxicity of methylmercury dissolved in corn oil versus water. Mallard (Anas platyrhynchos) and chicken (Gallus gallus) eggs were injected with methylmercury chloride dissolved in corn oil or water to achieve concentrations of 0, 0.2, 0.4, 0.8, and 1.6 μg/g mercury in the egg on a wet weight basis. Hatching success at each dose of mercury was compared between the two solvents. For mallards, 16.4% of the eggs injected with 1.6 μg/g mercury dissolved in water hatched, which was statistically lower than the 37.6% hatch rate of eggs injected with 1.6 μg/g mercury dissolved in corn oil, but no differences in hatching success were observed between corn oil and water at any of the other doses. With chicken eggs, no significant differences occurred in percentage hatch of eggs between corn oil and water at any of the mercury doses. Methylmercury dissolved in corn oil seems to have a toxicity to avian embryos similar to that of does methylmercury dissolved in water. Consequently, the results from the earlier study that described the toxicity of methylmercury dissolved in corn oil to avian embryos were probably not compromised by the use of corn oil as a solvent.