Iodine

Toxicity to birds

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to birds: reproduction test

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Although this study was conducted in turkeys which is not listed as a recommended species under OECD 206, this long term reproductive study was considered acceptable in the European Draft Assessment Report for Potassium Iodide. Furthermore, the NOEC from this study has been used for the risk assessment in this European report. As this study was not conducted to test guidelines a Klimisch score of 2 (reliable with restrictions) is considered appropriate.

Version / remarks:

Not indicated

Principles of method if other than guideline:

This purpose of this study was to determine the level of dietary iodine that would interfere with optimal egg production and hatchability of turkey eggs.

GLP compliance:

not specified

Specific details on test material used for the study:

Supplemental iodine was added to the diet as potassium iodide (KI). The potassium iodide was supplied by Fisher Scientific Company, Raleigh, NC 27629.

Dose method:

feed

Analytical monitoring:

yes

Vehicle:

no

Details on preparation and analysis of diet:

The birds received a basal diet which contained 0.7 mg iodine/kg (analysed) and were exposed to supplemental iodine, that was added as KI. KI was mixed into the feed and was analysed for actual iodine content. The iodine content was analysed by A & L Mid West Laboratories Inc. but the method of analysis is not stated.

Test organisms (species):

other: Meleagris gallopavo

Details on test organisms:

Large White turkey hens (Meleagris gallopavo) were hatched in December 1986 and 1987 and were grown to sexual maturity (30 weeks of age) on the North Carolina State University turkey research unit. The publication states that procedures using a Hybrid Management Manual were followed for the experiments.

Limit test:

no

Total exposure duration (if not single dose):

20 wk

Post exposure observation period:

None stated.

No. of animals per sex per dose and/or stage:

The number of hens per dose is not clear. However, there were 24 laying pens with 6 hens per pen, giving a total of 144 hens. Trial 2 had four dose groups, of which 18 breeder hens were used for each treatment (3 hens per pen) which means 72 hens were used in total. With the remaining 72 hens for Trial 1 (which had 3 dose groups) this suggests that 24 hens per dose were used in trial 1.

Control animals:

yes, plain diet

Nominal and measured doses / concentrations:

The birds received a basal diet which contained 0.7 mg iodine/kg (analysed) and were exposed to supplemental iodine, that was added as KI. Two trials were conducted:

Trial 1: The hens were assigned to one of three dietary iodine treatments by using a table of random numbers to form a randomised arrangement.

Treatments were:

Treatment 1: 0 ppm supplemental iodine in a basal ration (the composition is provided in the publication). The basal ration contains 0.7 ppm iodine.

Treatment 2: 2.1 ppm iodine supplemented as potassium iodide to the basal diet.

Treatment 3: 3.5 ppm iodine supplemented to the basal diet.

The basal diet contained no supplemental iodine and was calculated to contain 0.4 ppm from natural ingredients - the analysis indicated that the content of the basal diet was 0.7 ppm iodine. All of the remaining diets were shown to contain the calculated amount of iodine, which was measured to be within experimental error.

Trial 2: Treatments were 0, 3.5, 35 and 350 mg/kg supplemental iodine. The other main difference compared to trial 1 was that 18 breeder hens in each treatment ( 3 hens per pen) were bled via the ulnar vein into tubes containing 10 mg EDTA at 1, 10 and 20 weeks of egg production. Similar to trial 1, the basal diet contained 0.7 ppm iodine from ingredients and the treatment diets were analysed to contain levels within experimental error of the calculated levels.

Details on test conditions:

At 22 weeks of age, 144 hens were moved to a brooder building to a mechanically ventilated, light controlled facility and were exposed to 6 hours of incandescent light per day. At 30 weeks of age, the hens were moved to an open sided laying house with curtains. The hens were photo-stimulated to initiating lay by natural daylight that was supplemented with incandescent light each morning and night. This resulted in 15.5 hour days. Each pen had dimensions of 3.0 m x 2.4 m, which allowed 1.2 m2 of floor space per hen. Each pen consisted of two nests and 144 cm of waterer and feeder space.

Trial 1:

Feed samples were collected at mixing and were analysed for actual iodine content. Food and water was available to the test organisms ad libitum. Feed consumption and body weight were recorded at weekly intervals. After the start of oviposition, the eggs were collected five times per day and were recorded and labelled with a pen number and a date of oviposition. The eggs were sanitised and were stored at 12.8 degrees C and approximately 75% relative humidity for 0 to 7 days. At 1 day before setting, at weekly intervals, the eggs were sorted by pen and date of oviposition and warmed to room temperature overnight. The eggs were distributed randomly throughout the incubator. Three eggs were selected from each pen on the same day as oviposition, numbered and weighed to the nearest .01 g before setting. The eggs were weighed again at the time of transfer to the hatcher (25th day of incubation). The weight differences noted due to incubational egg water evaporation were used to estimate eggshell water vapour conductance. This procedure produced a sample size of 120 eggs per treatment per time period in Trial 1 and 90 eggs in Trial 2. At transfer, the weighed eggs were placed into pedigree baskets and poult weights of the weighed eggs were recorded at hatching (nearest .01 g). Relative poult weights were determined from the recorded egg and poult weights by dividing the hatching poult weight by the initial egg weight at setting. The hatchability was calculated on a pen basis. Following day 28 of incubation at 37.5 degrees C dry bulb and 30 degrees C wet bulb, the hatched poults were counted. The hatchability was computed by dividing the number of hatched poults by the number of fertile eggs. The non hatching eggs from each pen were broken down and examined for fertility and embryo morphoplogy. The purpose of this, was to estimate the time of embryo mortality.

Trial 2:

The conditions of Trial 2 were similar to that of Trial 1 in terms of the procedures and conditions described above. The differences in doses have been described under the "Nominal and measured doses/conditions" section above. The other difference was that 18 breeder hens per treatment (3 hens per pen) were bled from the ulnar vein into tubes that contained 10 mg EDTA at 1, 10 and 20 weeks of egg production. As there were 4 treatments in trial 2, the treatment sample size for statistical analyses was six pens, rather than eight in trial 1. Following collection, the blood samples were kept on ice for 30 minutes prior to centrifugation (700 x g at 4 degrees C) for 20 minutes. The plasma was decanted and frozen at -20 degrees C until a radioimmunoassay was conducted. The purpose of this assay was to measure blood plasma concentrations of thyroxine (T4) and triiodothyronine (T3). The hormone concentrations were statistically analysed at each of the three sampling times and were also pooled over the entire lay sample.

Details on examinations and observations:

Refer to above field "Details on test conditions".

Details on reproductive parameters:

Refer to above field "Details on test conditions".

Reference substance (positive control):

no

Duration (if not single dose):

20 wk

Dose descriptor:

NOEC

Effect level:

0.525 mg/kg bw

Conc. / dose based on:

test mat.

Mortality and sub-lethal effects:

No mortality was observed during the trials. Also in both of the trials, there was no significant differences in feed consumption or body weight observed.

Effects on reproduction:

Hatchability: Dietary iodine was found to affect the hatchability of turkey eggs. In trial 1, the 2.1 ppm treatment improved hatchability during weeks 11 to 15 of lay in comparison with the basal diet. However, over the 20 weeks of lay, this effect was not significant. Supplementing the basal diet with 3.5 ppm was also determined to improve hatchability during weeks 11 to 20 of lay. In trial 2, toxic effects of 35 ppm iodine were seen from 16 to 20 weeks of lay. Toxic effects at 350 ppm iodine were demonstrated by depressed hatchability at each 5 week period, also noted across the entire 20 weeks of lay. There were no significant positive effect on hatchability at the 3.5 ppm treatment, which is not consistent with the observations of trial 1.

Embryonic mortality: In trial 1, the 2.1 and 3.5 ppm dose groups decreased embryonic mortality (expressed as a percentage of fertile eggs) during the 1st week of incubation compared with the basal diet. The 3.5 ppm iodine dose group improved embryonic liveability during pipping, compared with the feeding of 2.1 ppm iodine to the basal diet. In trial 2, significant toxic effects of 350 ppm iodine on embryos were noted in weeks 1 and 2 of incubation, as well as during the plateau stage in incubation (days 25 and 26 of incubation, prior to breaking the shell) and during pipping (day 27 of incubation with pipped shell).

Egg production: The egg production based on hen-day performance was significantly affected during the 7th and 8th week of lay in the 0.7 and 3.5 mg/kg iodine treatments but not overall in the entire experiment (trial 1). In trial 2, the supplemental level of 350 mg/kg iodine depressed egg production at week 2 compared with other treatments and from the 11th week of lay until the end of the experiment, with the exception of week 14.

Initial egg mass: There were no significant differences observed in trial 1. In trial 2, the egg mass was significantly lower at 350 mg/kg iodine during the whole period. At 35 mg/kg iodine, decreased egg mass was observed during weeks 1-5 and weeks 11-15. At 3.5 mg/kg iodine, the egg mass was decreased during weeks 6-10 and 11-15. The pooled mean egg mass over the whole duration was significantly decreased at 35 and 350 mg/kg iodine.

Eggshell conductance: In trial 1, both the 2.1 and 3.5 mg/kg iodine treatments increased eggshell conductance compared to the basal diet. However, in trial 2 the increasing levels of dietary iodine decreased eggshell conductance in a dose related manner.

Hatchlings weight: In trial 1, the poult body weights at hatching were lower in the 2.1 and 3.5 mg/kg iodine treatments compared with those of the basal diet treatment. In trial 2, feeding 3.5 and 35 mg/kg iodine depressed poult weights at hatching, in comparison with the basal treatment. No differences due to iodine treatments were evident with respect to the poult weights relative to egg weight at setting.

Results with reference substance (positive control):

No positive control was used.

Reported statistics and error estimates:

The statistical analyses were performed using the General Linear Models procedure of the SAS Institute (reference is provided in the publication). The data were pooled by 5 week periods which accounted for effects due to the age of the breeder hen as well as for the entire 20 week trial. The square root of the arc sinc transformations were performed on all percentage data. The single factor in the model statement was treatment (0, 2.1 or 3.5 ppm iodine). Mean values that were determined to be significanly different were separated by Duncan's Multiple Range Test. Significance was based on a probability level of P ≤ 0.05.

Validity criteria fulfilled:

yes

Remarks:

Based on the European review which considered that this study is acceptable.

Conclusions:

In trial 1, there were no negative effects observed at the 3.5 mg/kg added iodine dose level. In trial 2, there were effects on hatchability at 35 mg/kg added iodine. Therefore the NOEC is considered to be 3.5 mg/kg fd. According to a conversion factor used in the European Draft Assessment Report, the daily food intake of adult birds is equivalent to 15% of their body weight. This gives a NOEC of 0.525 mg/kg bw/day for iodine.

Executive summary:

The purpose of this study was to determine the level of dietary iodine that would interfere with optimal egg production and hatchability of turkey eggs. Supplemental iodine was added to the diet as potassium iodide (KI) to large white turkey hens. Two trials were conducted, In trial 1, there were no negative effects observed at the 3.5 mg/kg added iodine dose level. In trial 2, there were effects on hatchability at 35 mg/kg added iodine. Therefore the NOEC is considered to be 3.5 mg/kg fd, equivalent to 0.525 mg/kg bw/day for iodine.

Although this study was conducted in turkeys which is not listed as a recommended species under OECD 206, this long term reproductive study was considered acceptable in the European Draft Assessment Report for Potassium Iodide. Furthermore, the NOEC from this study has been used for the risk assessment in this European report. As this study was not conducted to test guidelines a Klimisch score of 2 (reliable with restrictions) is considered appropriate.

Reference 2

Endpoint:

short-term toxicity to birds: dietary toxicity test

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

the study duration and the age of the test animals are consistent with the requirements of a standard 8 days dietary toxicity test

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 205 (Avian Dietary Toxicity Test)

Principles of method if other than guideline:

Chick bioassays were conducted to quantify iodine (I) toxicity and its amelioration in young chicks.

GLP compliance:

not specified

Dose method:

feed

Analytical monitoring:

not specified

Test organisms (species):

other: Gallus domesticus

Details on test organisms:

Experiments were carried out using color-sexed male New Hampshire x Columbian chicks. Chicks were housed in thermostatically controlled starter batteries with raised wire floors in an environmentally controlled building. Chicks were pretested on a fully fortified cornsoybean meal diet containing 23% crude protein (CP) until 1600 h of d 7 posthatching. On d 8 after being subjected to an overnight period of feed withdrawal, chicks were weighed, wing banded and randomly allotted to pens such that each pen of chicks had a similar initial weight and weight distribution. The average initial weight of chicks at trial initiation ranged from 86 to 95 g.

Limit test:

no

Total exposure duration (if not single dose):

13 d

Remarks:

Assay 1: 9 d (d 8 to 17); Assay 2: 13d (d 8 to 21)

Control animals:

yes, concurrent no treatment

Duration (if not single dose):

13 d

Dose descriptor:

LC50

Effect level:

> 1 500 mg/kg diet

Conc. / dose based on:

test mat.

Basis for effect:

mortality

Mortality and sub-lethal effects:

no mortalities in any of the experiments up to 1500 mg/I/kg fd (in the form of KI) over 13 days

Further details on results:

A supplemental I level from KI of 600 mg/kg depressed growth in chicks fed methionine-deficient diets but not in those fed methionine-adequate diets. An I dose level≥900 mg/kg was required to cause growth depression in chicks fed a methionine-adequate corn-soybean meal diet. Iodine intoxicated chicks also displayed neurological symptoms and extreme malaise, but dose levels up to 1200 mg I/kg had no effect on blood hemoglobin or hematocrit. Supplemental I levels of 1000 -1500 mg/kg caused severe growth depressions.

Reported statistics and error estimates:

- Statistical analyses. Pen means data were subjected to ANOVA procedures appropriate for completely randomized designs (22). Assay 1, (3×2×2 factorial), Assay 2 (graded I doses) were analyzed using orthogonal single df comparisons.

- Assay 1. Weight gain and food intake decreased (P<0.01) in a dose-dependent manner when graded doses of I were supplemented, and the I ×Met and I × protein level interactions were also significant (P﹤0.01) for these criteria Thus, the decreases in growth and food intake were steeper in chicks fed Met-deficient diets than in those fed Met-adequate diets, and in chicks fed diets with 180 g CP/kg than in those fed diets with 130 g CP/kg. Food efficiency decreased (P﹤0.01) linearly when 0, 600 and 900 mg I/kg were supplemented in Met-deficient diets, but food efficiency was not affected (P﹤0.10) by the 600 mg I/kg dose, and only modestly (P﹤0.05) by the 1200 mg I/kg dose, in chicks fed Met-adequate diets.

- Assay 2. Supplemental I was considerably less growth depressing when added to the corn-SBM diet, adequate in both CP and Met, than when added to the Met-deficient SBM semipurified diet used in Assay 1). Levels of supplemental I﹤600 mg/kg did not depress (P > 0.10) weight gain, but I levels ≥600 mg/kg reduced (P < 0.01) food intake. Remarkably, the gain:food ratio was not depressed by any level of supplemental I, and the same was true for both hemoglobin and hematocrit.

Validity criteria fulfilled:

not specified

Conclusions:

In this study, chicks (Gallus domesticus) that were administered up to 1500 mg/I/kg fd (in the form of KI) over 13 days resulted in no mortalities in any of the experiments. This is equivalent to a 13 day LC50 of > 1500 mg/I/kg fd.

Executive summary:

Chick bioassays were conducted to quantify iodine (I) toxicity and its amelioration in young chicks. A supplemental I level from KI of 600 mg/kg depressed growth in chicks fed methionine-deficient diets but not in those fed methionine-adequate diets. An I dose level≥900 mg/kg was required to cause growth depression in chicks fed a methionine-adequate corn-soybean meal diet. Iodine intoxicated chicks also displayed neurological symptoms and extreme malaise, but dose levels up to 1200 mg I/kg had no effect on blood hemoglobin or hematocrit. Supplemental I levels of 1000 -1500 mg/kg caused severe growth depressions.

In this study, chicks (Gallus domesticus) that were administered up to 1500 mg/I/kg fd (in the form of KI) over 13 days resulted in no mortalities in any of the experiments. This is equivalent to a 13 day LC50 of > 1500 mg/I/kg fd.

Reference 3

Endpoint:

long-term toxicity to birds: reproduction test

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 206 (Avian Reproduction Test)

Principles of method if other than guideline:

Iodine as potassium iodide was fed to sexually mature pullets and hens that had completed one year of lay, to study the effects upon egg production, fertility, hatchability, embryonic mortality and incubation time. Dietary intakes at 5 levels from zero to 5000 ppm iodine were fed in a practical-type diet for 6 weeks. Measurement of egg production was continued following the iodine feeding period.

GLP compliance:

not specified

Dose method:

feed

Analytical monitoring:

not specified

Details on preparation and analysis of diet:

The basal diet to which selected levels of iodine were added consisted of the following: (in per cent) ground yellow corn, 67.7; soybean meal, 20.6; alfalfa meal, 3.0; ground limestone, 5.8; defluorinated phosphate, 1.96; iodized salt, 0.4; and microingredients, 0.5. The microingredients supplied per kg diet: vitamin A, 4,400 IU; vitamin D3, 1,540 ICU; and (in milligrams) choline, 500; niacin, 13.2; riboflavin, 4.4; Ca pantothenate, 8.8; ethoxyquin, 12.5; MnSO4, 220; and (in micrograms) vitamin B12, 13.2.

Test organisms (species):

other: White Leghorn pullets and White Leghorn hens

Details on test organisms:

One hundred and fifty 27-weekold White Leghorn pullets and One hundred mature White Leghorn hens which had been in production for 12 months

Limit test:

no

Total exposure duration (if not single dose):

6 wk

Post exposure observation period:

27 week

No. of animals per sex per dose and/or stage:

Pullets: 30
Hens: 20

Control animals:

yes, concurrent no treatment

Nominal and measured doses / concentrations:

Nominal:
Pullets: zero, 625, 1250, 1875 or 2500 ppm, Four additional replicate treatments of 5 pullets each were provided with 5000 ppm iodine for 105 days.
Hens: zero, 625, 1250, 1875 or 2500 ppm

Egg production of pullets fed iodine varied inversely with level of iodine beginning during the first week of treatment. With 5000 ppm iodine, virtually no eggs were produced after the second week. Pullets fed the control diet maintained a production rate of 75% or more throughout the 6-week experimental period.

No molting accompanied the cessation of lay, and production increased rapidly after removal of dietary iodine. At the end of the 6-week period, production of pullets fed 2500 ppm iodine was 13% that of controls. By one week after iodine was re moved, production equaled approximately 80% that of controls. The rate of production during 27 weeks after removal of iodine was not significantly different from controls. Two pullets in the group fed 2500 ppm iodine failed to return to production. At the end of the 27-week period, they were killed and eggs with several membranes were found in the isthmus. Tumerous growths present were evidently preventing their passage. This condition was not considered to be caused by iodine and these pullets were not included in the calculation of egg production data. If these 2 pullets had been included, the rate of production would have been 51.8 instead of 56.3%.

Pullets provided 5000 ppm iodine were continued for 15 weeks and remained out of production. When returned to the control diet, all except one returned to production within 10 days. The rate of production for 16 weeks, beginning 2 weeks after removal of iodine, was 51.7% compared with 51.6% for the control group.

Mature hens responded somewhat differently to iodine treatment than pullets although the major effects were similar. The hens were removed from floor pens to laying cages at one week before iodine was fed. A small percentage of the hens in each group molted, but the proportion in the control group was less than in the iodine groups. Sixty-eight per cent of all hens fed iodine were out of production after one week and by 4 weeks, 95% had ceased laying. Only 40% of the control hens were out of production at that time. When the iodine was removed from the diet, they returned to production in a manner similar to that observed for pullets. The rate of production for these hens was equal to that of the controls for an 18-week period beginning 2 weeks after removal of iodine from the feed. Physical condition of pullets and hens out of production was such that they would have been judged to be laying. Position of the pelvic bones indicated production and yellow pigment was absent from beaks and shanks. Ovaries of hens not laying contained many ova in various stages of development but ovulation was not occurring. Some ova appeared to be regressing. The ovary labeled 5000 ppm was from a hen which had been out of production for 5 weeks.

Average of individual weights of eggs produced by the pullets fed all levels of iodine were significantly less than that of controls. At 3 weeks after removal of iodine, egg weights were normal. Interior quality of the eggs was improved following the rest induced by iodine in the mature hens. Average Haugh units of eggs from control hens maintained in continuous production was 62.6. The average value for eggs produced by hens at 10 weeks after removal from 2500 ppm iodine was 70.4.

Fertility of eggs produced was not affected by iodine feeding, but hatchability was decreased and embryonic mortality and length of hatching time increased. The percentage hatchability de creased with increasing levels of iodine and was considerably less with eggs produced near the end of the iodine feeding period. Approximately 80% of all embryonic deaths occurred within the first 4 days of incubation. A number of the embryos survived the incubation period and pipped the shell, but were unable to emerge. Hatching time was delayed by 24 hours or more in 20 to 100% of the eggs hatched from hens fed iodine. Some eggs were hatched following a delay of more than 96 hours.

Thyroid weights of the chicks from hens fed 2500 ppm iodine were 3 times larger than those of controls but no specific differences in microstructure were observed.Hatching weight of the chicks was not affected by iodine, but the chicks from the iodine group appeared weak and did not grow as well as controls. Control chicks averaged 88.5 g body weight at 2 weeks of age and those from pullets fed 2500 ppm iodine averaged 68.7 g.

Relatively few eggs were available for incubation from mature hens and none were produced near the end of the iodine feeding period. Those which were collected early after iodine feeding was started and were incubated, indicated the same effects upon hatchability as observed in pullets.

Validity criteria fulfilled:

not specified

Conclusions:

Egg production decreased with increasing levels of iodine and ceased with intakes of 5000 ppm. The decreases were greater for hens than for pullets. Production commenced and increased rapidly within one week after change to control diets and was equal to that of control birds during a 27- and 18-week subsequent feeding period for pullets and hens. Molting did not accompany the cessation of lay in pullets but some mature hens molted. Mature ova were present in birds not laying but ovulation did not occur. Weight of eggs produced during the period of iodine feeding was reduced but returned to normal within 3 weeks. Fertility of eggs was not affected but high embryonic death, low hatchability and delayed hatching were observed.

Executive summary:

Iodine as potassium iodide was fed to sexually mature pullets and hens that had completed one year of lay, to study the effects upon egg production, fertility, hatchability, embryonic mortality and incubation time. Dietary intakes at 5 levels from zero to 5000 ppm iodine were fed in a practical-type diet for 6 weeks. Measurement of egg production was continued following the iodine feeding period.

Egg production decreased with increasing levels of iodine and ceased with intakes of 5000 ppm. The decreases were greater for hens than for pullets. Production commenced and increased rapidly within one week after change to control diets and was equal to that of control birds during a 27- and 18-week subsequent feeding period for pullets and hens. Molting did not accompany the cessation of lay in pullets but some mature hens molted. Mature ova were present in birds not laying but ovulation did not occur. Weight of eggs produced during the period of iodine feeding was reduced but returned to normal within 3 weeks. Fertility of eggs was not affected but high embryonic death, low hatchability and delayed hatching were observed.

Description of key information

Short term toxicity to birds (13 days, chicks): LC50 >1500 mg/kg fd (> 197 mg/kg bw/day)

Long term reproductive toxicity to birds (20 weeks, turkeys): NOEC 3.5 mg/kg fd (0.525 mg/kg bw/day)

Key value for chemical safety assessment

Short-term EC50 or LC50 for birds:

1 500 mg/kg food

Long-term EC10, LC10 or NOEC for birds:

3.5 mg/kg food

Additional information

There are existing data available on the toxicity of iodine to birds, that has been reviewed in the European Draft Assessment Report for Potassium Iodide. The studies that were assessed in the European review are publically available and have been obtained separately to support the registration of iodine under REACH. The European review of these studies has been summarised below, where appropriate.

Long term/reproductive toxicity to birds

The key data that is assessed in the endpoint summary is a long term reproductive toxicity study to birds (20 weeks, turkeys; Christensen, V.L. and Ort, J.F. 1991) which derived a NOEC of 3.5 mg/kg fd. According to a conversion factor used in the European Draft Assessment Report, the daily food intake of adult birds is equivalent to 15% of their body weight. This gives a NOEC of 0.525 mg/kg bw/day for iodine.

Although this study was conducted in turkeys which is not listed as a recommended species under OECD 206, this long term reproductive study was considered acceptable in the European Draft Assessment Report for Potassium Iodide. Furthermore, the NOEC from this study has been used for the risk assessment in this European report. As this study was not conducted to test guidelines a Klimisch score of 2 (reliable with restrictions) is considered appropriate. This study is therefore considered to meet the REACH data requirements in Annex X. For details on other data that were not used in the European review for risk assessment purposes, see the reference below.

Acute toxicity data to birds

Although this data is not a REACH requirement, there is information available that has been assessed in the European Draft Assessment Report for Potassium Iodide, that has data relevant to iodine. For full details on the assessment, refer to the European review. Data from Baker (2004) noted that potassium iodide is not acute toxic at dietary iodine doses up to 900 mg I/kg bw. However, the European review noted that the available data does not meet the quality criteria normally applied for risk assessment. Other data from Arrington et al. (1967) contained a number of deficiencies, and the non lethal concentration from this 6 week study could not be used as a substitute for an acute LD50. The best available data (Baker et al., 2004) indicates that the acute LD50 for iodine in birds is > 900 mg I/kg bw.

Short term toxicity

Although this data is not a REACH requirement, there is information available that has been assessed in the European Draft Assessment Report for Potassium Iodide, that has data relevant to iodine. For full details on the assessment, refer to the European review. Data from Baker et al., (2003) was considered appropriate in the European review as the study duration and the age of the test animals are more consistent with the requirements of a standard 8 days dietary toxicity test. In this study, chicks (Gallus domesticus) that were administered up to 1500 mg/I/kg fd (in the form of KI) over 13 days resulted in no mortalities in any of the experiments. This is equivalent to a 13 day LC50 of > 1500 mg/I/kg fd. Based on the calculations by the RMS, this is equivalent to an LC50 of >197 mg/kg bw/day (for iodine).

References:

Arrington, L.R., Santa Cruz, R.A., Harms, R.H, Wilson, H.R. (1967) Effects of excess dietary iodine upon pullets and laying hens. Journal of Nutrition 92: 325 - 330

 

Baker, D.H., Parr, T.M., Augspurger, N.R. (2003) Oral iodine toxicity in chicks can be reversed by supplemental bromine. Journal of Nutrition 133: 2309-2312

 

Baker, D.H. (2004) Iodine toxicity and its amelioration. Experimental Biology and Medicine 229: 473 -478

 

Christensen, V.L., Ort, J.F. (1991) Iodine toxicity in large white turkey breeder hens. Poultry Science 70, 2402-2410

 

European Commission, (2008) Draft Assessment Report (DAR) – public version – Initial risk assessment provided by the rapporteur Member State The Netherlands for the new active substance Potassium Iodide (of the review programme referred to in Article 8(1) of Council Directive 91/414/EEC.

Downloaded from:

http://dar.efsa.europa.eu/dar-web/provision