4.11 Lindane (048)(R)**

R-residue and analytical aspects

** Evaluated within the Periodic Review Programme of the Codex Committee on Pesticide Residues

RESIDUE AND ANALYTICAL ASPECTS

Lindane, a broad-spectrum insecticide, was originally evaluated by the JMPR in 1966 (under the name gamma-BHC) and re-evaluated for residues several times up to 1989. Lindane was scheduled for residue review by the 2003 JMPR under the Periodic Review Programme by the 30th Session of the CCPR (ALINORM 99/24).

At the 31st Session of the CCPR several delegations preferred revocation of the MRLs for lindane as (1) the TMDI greatly exceeded the temporary ADI; (2) it had been banned in many countries; (3) it has limited uses and (4) its last evaluation was in 1989. It was decided that at its next Session the Committee would consider the revocation of the existing CXLs, "(except those accompanied by the letter F)", if not supported. The company confirmed support for cereals, sugar beet, maize and oil seed (sunflower and canola).

The Meeting received information on identity, metabolism and environmental fate, residue analysis, use pattern, residues resulting from supervised trials on wheat and canola, fate of residues during processing, animal feeding studies, and residues in food in commerce or at consumption. In addition information on GAP and/or national MRLs was supplied by the governments of Australia, Germany, The Netherlands, Poland and the USA.

Animal metabolism

The Meeting received information on metabolism in orally-dosed lactating goats, laying pheasants and laying hens. All studies were with uniformly-labelled [¹⁴C]lindane.

Studies on metabolism in mice, rats, rabbits and dogs evaluated by the WHO Core Assessment Group of the 2002 JMPR indicated that lindane undergoes extensive metabolism in animals. Stepwise dehydrogenation, dechlorination, and dehydrochlorination may be followed by conjugation with sulfate or glucuronide. Lindane itself was considered to be the toxicologically significant compound.

Lactating goats. Animals dosed orally with [¹⁴C]lindane at doses of 13, 20 or 200 ppm in the feed excreted 34-46% of the administered ¹⁴C in the urine, 5.1%-13% in the faeces, and 1.1%-2.4% in milk, and 4.0%-4.4% was found in the tissues. The highest radioactive residues were found in body fat, followed by liver, kidney and muscle. 0.2%-1.0% of the administered radioactivity was recovered as expired ¹⁴CO₂. Total recoveries for each goat were low (51%-59%), probably owing to loss of volatile ¹⁴C-metabolites untrapped by the solutions.

In fat and muscle, ¹⁴C was mainly in the parent compound (73-85% and 28-81% of the TRR, corresponding to about 3 mg/kg and 0.02-0.16 mg/kg respectively at the lower doses). The metabolites identified in fat were 1,2,4-trichlorobenzene (3.6-11%), g-pentachlorocyclohexene (5.8%), 1,2,4,5-tetrachlorobenzene (0.8-1.5%), 1,2,3,4,5,6-hexachlorocyclohexene (0.4-0.7%), and 1,2,3,4-tetrachlorobenzene and 1,2,3,5-tetrachlorobenzene (each <0.1%), and in muscle 1,2,4-trichlorobenzene and g-pentachlorocyclohexene (5.8% and 3.5% of the TRR respectively).

In liver and kidney the parent compound constituted only about 16% and 4.5-36% of the TRR respectively, corresponding to about 0.36 mg/kg and 0.17 mg/kg at the 13 ppm feed level. In liver all individual components were £1.3% of the TRR (or 0.029 mg/kg eq). Identified, although not quantified, were 1,3,5-trichlorobenzene, 2,6-dichlorophenol and 2,3,4,5-tetrachlorophenol, and tentatively 2,3,4-trichlorophenol. In kidney, g-tetrachlorocyclohexene and possibly 1,2-dichlorobenzene were identified at 4.5% and 5.8% of the TRR respectively.

In milk residues reached a plateau after 2-3 days. Approximately 55-87% of the TRR in whole milk was in the fat. Lindane was the major constituent in milk fat (55%-77% of the TRR of whole milk; 0.11 mg/kg at the 13 mg ai/kg feed level) with 1,2,4-trichlorobenzene up to 16% of the TRR and g-pentachlorocyclohexene at about 5% of the TRR of whole milk. Skimmed milk contained 6-8 conjugated chlorophenols (5.9%-17% of the TRR of whole milk).

Laying hens. In this study 44-63% of the total applied radioactivity (TAR) was recovered from the excreta, 2.6-9.0% from eggs and 20-47% from tissues and organs. Total recovery of the administered radioactive dose was above 90%. The highest concentration of residues was found in the fat (5.5-13% of the TAR), followed by skin (5.5-10% of the TAR), thigh muscle (1.8-3.0% of the TAR), liver (0.43-0.97% of the TAR), breast muscle (0.2-0.5% of the TAR) and kidney (0.09-0.26% of the TAR).

Lindane was the main residue in all tissues analysed: fat 85%, thigh muscle 71%, liver 51%, breast muscle 100%, egg yolk 94%, egg white 100% of the identified residues. In breast muscle and egg whites no radioactive residue other than the parent was identified, whereas in fat and egg yolks the main metabolite was 2,3,4,5,6-pentachlorocyclohexene (6.1% and 4.2% of the identified residues respectively), and in liver 1,2,4-trichlorobenzene (19% of the identified residues) while dichlorobenzenes were present at 9.5% and 1,3,5-trichlorobenzene at 6.4%. In thigh muscle the main metabolite was 1,2,4,5- or 1,2,3,4-tetrachlorobenzene (18% of the identified residues). All other metabolites identified were £5% of the TRR. During the dosing period (4-6 days) no plateau was reached in eggs.

Laying hen pheasants were dosed for 15 days. Eggs were collected daily for about 70 days for analysis. Residues in the yolks were highly variable, increasing sharply and reaching a mean maximum level in 8 days in a group dosed with capsules and gradually in a group fed treated seed reaching a mean maximum in 22 days. Thereafter levels decreased gradually to <0.5 mg/kg eq in both groups (in about 50 days in the former and about 70 days in the latter).

The metabolism of lindane in laboratory animals was qualitatively similar to that in farm animals.

Plant metabolism

The Meeting received information on the fate of lindane in plants grown from lindane-treated seeds, in spinach and cucumber plants after post-emergence spray applications and in apples after pre-harvest spray applications. The studies were conducted with uniformly-labelled [¹⁴C]lindane.

Wheat seeds coated with lindane at an actual rate of 480 g ai/t were planted in the field and the resulting crops sampled 19 and 100 days after treatment. Significant amounts of residues were present in the seedlings and in the mature plants, indicating that lindane and/or its degradation products are readily translocated into growing plants. Extraction of the plant tissues with MeOH recovered more radioactive residues from the seedlings (91% of the TRR) than from any part of the mature plants (63% of the TRR from roots, 67% from straw, 34% from chaff), indicating that radioactive residues are more strongly bound in mature plant tissues.

No radioactive residue could be detected in grain. The parent was found at 36% of the TRR (0.2 mg/kg eq) in seedlings, 21% (0.48 mg/kg eq) in roots and 5.4% (0.006 mg/kg eq) in straw, and was undetected in chaff. In the seedlings, 26% of the TRR (0.14 mg/kg eq) was hydrophilic and 29% (0.16 mg/kg eq) hydrophobic. The proportion of the hydrophilic compounds increased in the mature plants: 27.4% of the TRR (0.63 mg/kg eq) in the roots, 53% (0.06 mg/kg eq) in the straw and 34% (0.007 mg/kg eq) in the chaff. Roots contained eight non-acidic compounds (chlorobenzenes), each £5.7% of the TRR (0.13 mg/kg eq), and four acidic compounds (chlorophenols).

Radish, sugar beet, spinach, mustard, maize, sweet corn, and spring wheat seeds were coated with uniformly-labelled [¹⁴C]lindane (actual dose rates 380, 2290, 820, 590, 1770, 1440 and 370 g ai/t respectively) and planted outdoors under a clear protective roof. Sugar beet plants did not reach full maturity. Significant residues (>0.01 mg/kg eq) were found in all crop parts, except maize cobs and grains. The highest levels of radioactivity were found in spring wheat samples (foliage > grain > roots). Mustard seeds were not analysed.

Residues were extracted with acetonitrile (ACN) and analysed for lindane. In the ACN extracts of the fast-growing crops 81% of the TRR (mustard foliage) and 54% of the TRR (radish roots) was identified as the parent.

In the slow-growing crop extracts lindane constituted 30% of the TRR (0.09 mg/kg) in sugar beet roots, 19% (0.04 mg/kg) in sugar beet foliage, 20% (0.16 mg/kg) in maize roots, 12% (0.008 mg/kg) in maize foliage, 24% (0.012 mg/kg) in sweet corn foliage, 0.5% (0.016 mg/kg) in spring wheat foliage and 3.8% (0.002 mg/kg) in spring wheat grain. It should be noted that virtually all of the radioactivity in spring wheat foliage (109%; 3.2 mg/kg) and grain (217%; 0.11 mg/kg eq) was unextracted. (The author's figures are quoted although clearly in error; no explanation was suggested.)

A single Red Delicious apple tree was treated once with 1 kg ai/ha uniformly-labelled [¹⁴C]lindane, just before petal fall. Lindane and metabolites were found in both leaves and fruit. The presence of lindane in the fruit indicate that it was distributed throughout the tree and transferred to the maturing fruit from the leaves and twigs. Total radioactive residues decreased during the maturation period and those in the apples were about one fifth of the levels in the foliage at each collection. The amount of unextracted residue increased with time from about zero initially to 30-40% of the TRR in the foliage and 25% of the TRR in the mature fruit.

At harvest at 131 days, radioactive residue in foliage consisted of 3.2% of the TRR of lindane, minute quantities of chlorinated phenols (2.0% of the TRR), TLC-origin material (19% of the TRR), water-soluble material (40% of the TRR) and unextracted residues (32% of the TRR). Residues in the fruit consisted of 11% of the TRR as parent, 14% as pentachlorophenol, minute quantities of two other chlorinated phenols (0.6% of the TRR), TLC-origin material (12% of the TRR), water-soluble material (38% of the TRR) and unextracted residues (25% of the TRR). In mature apples the levels of unextracted residues and residues in the aqueous layer were too low (<0.02 mg/kg eq) to justify further investigation.

Fenumex cucumber plants were treated three times with EC foliar applications of [¹⁴C]lindane at a rate of 0.71 kg ai/ha each. Autoradiography indicated that radioactivity spread very rapidly throughout the plant. Radioactivity in the stem and root detected immediately after treatment disappeared after 24 h, and after seven days most had disappeared from the leaves.

Most of the radioactivity was in the leaves and extractable radioactivity decreased rapidly. Growth dilution appeared to be important in reducing the residue on a weight/weight basis. Residues in cucumber fruits ranged from 0.00009-0.0032 mg/kg eq and were therefore not further investigated. In the initial plant extracts that contained sufficient radioactivity no radioactive components co-eluted with potential metabolites, including chlorinated benzenes, cyclohexanes, and phenols (it was not stated which were used as reference standards). Lindane was the only residue identified. Hydrolysis of the solids released additional radioactivity consisting of multiple low-level radioactive components.

Separate recovery studies were conducted on a cucumber plant grown in an aerated glass enclosure. Volatiles were collected in traps for CO₂ and volatile organic compounds. Radioactivity at 7 days was distributed among leaves (41% of the TAR), stems (3.9% of the TAR), roots (0.9% of the TAR), soil (14% of the TAR) and traps (17% of the TAR) or remained stuck to tanks, tubes and pots (27% of the TAR).

Perpetual spinach plants at the two-leaf stage were treated with a single foliar application of uniformly-labelled [¹⁴C]lindane at a rate of 1.5 kg ai/ha. Autoradiography showed that lindane was translocated rapidly throughout the plants. At 1 day no radioactivity was associated with the roots and at 7 days the greater part of the residue had disappeared from the leaves. Total radioactive residues (TRR) had decreased markedly by day 7 to below 1% of the TAR. By the time the plants matured (60-92 days) the TRR was at most 0.0004 mg/kg eq, too low to allow identification of metabolites. In acetone extracts of immature plants at 0, 1 and 3 days, lindane was the only radioactive component observed.

Lindane is intended for use as a seed treatment on oilseeds and cereal grains. After seed treatment, significant amounts of residues were present in the seedlings and in the mature plants, indicating that lindane and/or its degradation products are readily translocated. Extraction efficiency decreased when plants matured indicating that radioactive residues are more strongly bound in the mature plant tissues. This is also consistent with the fact that lindane was a major residue in fast-growing crops, but its contribution decreased in slow-growing crops. In one study on wheat plants grown from seeds treated with lindane according to GAP, no radioactivity could be detected in the grain at harvest. In a second study, only 0.052 mg/kg eq radioactive residue was found in the wheat grain, of which virtually all (217% according to the author's figures) was unextractable. Of the very small amount extracted, 3.8% of the TRR (corresponding to 0.002 mg/kg eq) was the parent compound. Also in wheat foliage at harvest, only about 5% of the radioactive residue was extractable, corresponding to 0.14 mg/kg equivalents. Of this, 10% (0.016 mg/kg) was identified as the parent compound.

All metabolites found in plants were also characterized in animals.

Environmental fate in soil

In a field rotational crop study soil was treated with [¹⁴C]lindane at a rate of 0.85 kg ai/ha as an EC formulation in a spray volume of 700 l/ha before planting. Lindane was incorporated to a depth of 5 or 10 cm. Soil cores (30 cm in depth) were collected before and immediately after treatment, at each crop planting, and at harvest. Subsequently each core was divided into 0-15 and 15-30 cm sub-cores. Walmann's Green Leaf lettuce, Goldmine carrots, and BB882 barley were planted 30 days, 121 days and 365 days respectively after spraying.

With one exception, the 15-30 cm sub-cores contained TRRs of £0.01 mg/kg eq, so only the 0-15 cm sub-cores were extracted with acetone. Lindane was the only component found to be extractable, at 28-88% of the TRR, suggesting that the rotational crops were exposed only to lindane and soil-bound (unextracted) residues. Lindane was found to be rather persistent in soil: 73% of the parent compound found 2 h after treatment was still present 240 days later. The TRR in crops did not appear to be strongly related to the TRR in soil. An approximately linear relationship between crop and soil TRR levels was observed only in mature barley grain and straw. In mature lettuce plants, radioactive residues decreased with increasing plant-back intervals, from 0.04 mg/kg eq at 30 days to 0.009 mg/kg eq at 365 days. 43% of the TRR was identified as lindane, 19% as 3 different chlorophenols, and 35% was unextracted.

In mature carrot roots the amount of radioactive residue remained constant at the different plant-back intervals at 0.4 mg/kg equivalents Approximately 86% of the TRR was identified as lindane, 4.4% as 1,3,4,5,6-pentachlorocyclohexene, 3% was unidentified and 1.7% was unextracted.

In barley forage, 0.10-0.4 mg/kg eq radioactive residue was found at the different plant-back intervals, of which 16-26% of the TRR was lindane, about 9% was 3 different chlorophenols, 39-52% was unextracted, and 17-18% was unidentified. In barley grain, radioactivity (0.05-0.09 mg/kg eq) was either unextracted (71-112% of the TRR) or uncharacterized (0-32% of the TRR). About half of the uncharacterized radioactivity could later be attributed to 3 different chlorophenols. In barley straw, 68-78% of the TRR (0.1-0.9 mg/kg eq) was unextracted, 11-34% was uncharacterized, 0.36-2.4% was lindane, and about 4% was 3 different chlorophenols.

At each sampling lindane degradation products, if present in soil, were too low to quantify so only lindane was available for uptake, and degradation products in crops arose from metabolism of lindane within the plants. The metabolites identified in crops from the rotational study are among those identified in the seed-treatment metabolism study on wheat, confirming that degradation of lindane taken up by roots proceeds by hydroxylation and successive losses of chlorine.

Environmental fate in water-sediment systems

Solutions of 1 mg/l uniformly-labelled [¹⁴C]lindane at pH 5, 7 and 9 at two ionic strengths were kept in the dark at 25 ± 1°C for 30 days. At pH 5 and 7 lindane was stable with a half-life of 115-173 and 282-309 days respectively, with 5% transformation after 30 days. At pH 9, lindane was unstable with a half-life of 35-36 days. After 30 days, 43-44% transformation was found with 7% 2,3,4,5,6-pentachlorocyclohexene and 4% trichlorobenzenes (1,2,4- and 1,2,3-), and 32-33% not accounted for.

In water as well as in an acetone-sensitized aqueous solution, [¹⁴C]lindane was resistant to natural sunlight. After 28 days recovery was comparable to the dark control and no degradation products were observed. Lindane was also resistant to simulated sunlight. After 15 days irradiation equivalent to 44.5 days of natural sunlight at 40° N in summer, in water at pH 7 at 25°C, recovery was ³92% (dark control ³91% recovery). Again no degradation products were observed.

It was concluded that lindane is resistant to hydrolysis (except at high pH) and photolysis.

Methods of analysis

Analytical methods proposed as enforcement methods, and those used in supervised residue trials, storage stability studies, processing studies and feeding studies were reported.

Two enforcement methods were reported. A Dutch multi-residue method for fruit and vegetables involves extraction by a method for non-fatty samples and GC with ion-trap detection with an LOQ of 0.03 mg/kg. The AOAC method is a multi-residue method for organochlorine and organophosphorus pesticide residues and is suitable for non-fatty foods, dairy products and whole eggs. After extraction lindane is quantified by GC with ECD or KCl-thermionic detection. The LOQ was not stated.

Method 109, a GC-MS method, was used in supervised trials, storage stability studies and processing studies on wheat and canola. The reported LOQ was 0.005 mg/kg in wheat and canola commodities.

Modified AOAC methods were used in feeding studies on poultry, cows, sheep and pigs and storage stability studies on animal commodities. Reported LOQs were 0.01 mg/kg for liver, kidney, muscle and fat, 0.001 mg/kg for milk and 0.005 mg/kg for eggs, but the validated LOQs were liver and kidney 0.05 mg/kg, muscle 0.02 or 0.03 mg/kg, milk 0.005-0.2 mg/kg, and eggs 0.1 mg/kg.

Stability of residues in stored analytical samples

The Meeting received data on the stability of residues in wheat forage, hay, straw and grain, in canola seed, meal and refined oil, and in animal tissues, eggs and milk stored frozen.

Lindane residues in wheat and canola were stable at -20°C for the time tested (wheat forage 14 months, wheat hay, wheat straw and wheat grain 18 months, canola seed 6 months, canola meal 1.5 months, refined canola oil 1.8 months).

Lindane was stable at -18°C for 9 months in animal tissues and for at least 12 months in milk and eggs.

Definition of the residue

In goat fat and muscle, the residue was mainly present as the parent compound (82-86% and 62-90% of the TRR respectively). In goat liver and kidney, the parent compound was present at 0.4-16% and 4.7-36% of the TRR respectively. Approximately 55-87% of the TRR in whole milk was associated with the milk fat where lindane was the major constituent (55%-77% of the TRR of whole milk). In laying hens lindane was the major radioactive residue in all tissues tested: fat 87%, thigh muscle 77%, liver 39%, breast muscle >100%, egg yolk >100%, egg white 67% of the TRR. In breast muscle and egg white, no radioactive residue besides lindane was identified.

Since the parent compound is the major residue in all animal commodities, and since the remaining residue is made up not of one single component but of a wide range of chlorocyclohexenes, chlorobenzenes, and chlorophenols, the Meeting agreed that the parent is a suitable marker molecule for enforcement in animal commodities and is also the compound of interest for dietary risk assessment.

The log K_ow of lindane is 3.2-3.7. Taking into account results from farm animal feeding studies, the Meeting concluded that lindane should be classified as fat-soluble.

Lindane is intended for use as a seed treatment on oilseeds and cereal grains. As discussed in the section on plant metabolism, after pre-planting seed treatment virtually all the radioactive residue in wheat grain (>100% of the TRR) and wheat foliage (95% of the TRR) at harvest is unextractable.

In view of the low levels of radioactive residue present at harvest (0.052 mg/kg eq in grain), the lack of an alternative marker molecule, the fact that lindane was considered to be the toxicologically significant compound, and the fact that the existing definition of the residue is lindane, the Meeting agreed that the definition of the residue for compliance with MRLs and for estimation of dietary intake should be:

lindane, for both plant and animal commodities.

The residue is fat-soluble.

Supervised residue trials

Trials were reported on wheat and canola.

Root and tuber vegetables (group 016)

There is a current CXL for carrot of 0.2 E mg/kg, which stems from 1977 and was based on a rotational crop study. The rotational crop study described above confirms that carrots can take up relatively large amounts of the parent compound. Since neither information on GAP nor supervised trials on carrots were reported, the Meeting decided to recommend withdrawal of the existing CXL for carrot.

Neither information on GAP nor supervised trials were reported for sugar beet. The Meeting decided to recommend withdrawal of the current CXLs for sugar beet and sugar beet leaves or tops, both 0.1 mg/kg.

Cereal grains (group 020)

Lindane is registered in Canada and the USA for use on barley, maize, sweet corn, oats, rye, sorghum and wheat with DS, LS, FS, and ES formulations with a single treatment of the seeds immediately before sowing. Fifteen residue trials on wheat were conducted in the USA (1997, 1998) using an application rate of 328 g ai/t. In the USA, there are 13 labels for use on wheat. On 12 of those the application rate ranges from 163 to 391 g ai/t, but on one label the application rate is 2085 g ai/t and therefore the trials cannot be considered to be at the maximum US GAP.

In Canada two labels for use on wheat are registered; the critical label specifies an application rate of 390 g ai/t, so all 15 US trials were according to maximum Canadian GAP. Residues in wheat grain were all <0.005 mg/kg.

From the rotational crop study it became clear that the behaviour of lindane in barley is comparable to that in wheat. The metabolism study with several lindane-treated seeds showed that wheat grain and foliage contained more lindane than maize grain and foliage. Therefore the Meeting decided to extrapolate the results from the supervised trials in wheat to all registered pre-planting seed treatments of lindane on cereal grains, i.e. barley, maize, sweet corn, oats, rye, and sorghum.

The Meeting estimated a maximum residue level of 0.01* mg/kg in wheat, barley, maize, sweet corn, oats, rye and sorghum, with STMRs and HRs of 0.005 mg/kg.

Oilseeds (group 023)

Lindane is registered for use on mustard in Canada. Six residue trials on canola were conducted in the USA (1998), but no relevant GAP was available for evaluation of the data.

The Meeting decided to recommend withdrawal of the current CXL for rape seed of 0.05* mg/kg.

Straw, fodder and forage of cereal grains and grasses (group 051)

The wheat trials that were evaluated for grain residues were also evaluated for residues in wheat forage, hay and straw. The results were again extrapolated to barley, maize, sweet corn, oats, rye and sorghum.

Residues in wheat forage were <0.005 (8), 0.0087, 0.0097, 0.014, 0.017, 0.021, 0.032 and 0.036 mg/kg.

The Meeting estimated a highest residue level of 0.036 mg/kg in wheat, barley, maize, sweet corn, oat, rye and sorghum forage, and an STMR of 0.005 mg/kg.

Because of matrix interferences in wheat hay up to 0.0037 mg/kg, the reported LOQ for wheat hay should be increased to 0.01 mg/kg. Taking this into account, residues in wheat hay were <0.01 (14) and 0.023 mg/kg.

The Meeting estimated a highest residue level of 0.023 mg/kg in wheat, barley, maize, sweet corn, oats, rye and sorghum hay, and an STMR of 0.01 mg/kg.

Residues in wheat straw were <0.005 (15) mg/kg.

The Meeting estimated a maximum residue level of 0.01* mg/kg in wheat, barley, maize, sweet corn, oats, rye and sorghum straw, with STMRs and HRs of 0.005 mg/kg.

Fate of residues during processing

The Meeting received information on the fate of residues in the processing of canola seeds to oil.

Canola seeds with incurred residues were processed on a small scale into meal, refined oil and edible oil. No residues could be detected in seed, meal or edible oil, but a residue of 0.013 mg/kg was found in the refined oil. Because no residues were found in the seed, processing and transfer factors could not be calculated.

Farm animal dietary burdens

The Meeting estimated the dietary burden of lindane residues in farm animals from the diets listed in Appendix IX of the FAO Manual (FAO, 2002). One feed commodity only from each Codex Commodity Group is used. Calculation from the MRLs or HR values provides the concentrations in feed suitable for estimating MRLs for animal commodities, while calculation from the STMRs for feed is suitable for estimating STMRs for animal commodities. In the case of processed commodities, the STMR-Ps are used for both calculations.

Maximum farm animal dietary burden

Mean farm animal dietary burden

Farm animal feeding studies

Animal feeding studies were reported for dairy cattle, sheep, pigs and chickens. In all the studies, only the parent compound was determined.

Three milking Holstein cows were dosed orally with lindane at levels equivalent to 20, 60 or 200 ppm in the feed. Dosing took place for 28 days after the morning milking (by gelatin capsule using a balling gun). Milk samples were taken on days 1, 3, 7, 14, 21, 25 and 28. Animals were slaughtered 20 h after the last dosing. Residues in fat were 12, 20 and 158 mg/kg for the 20, 60 and 200 ppm cows respectively. Residues in muscle were 0.97, 1.8 and 8.8 mg/kg, in liver 0.10, 0.19, and 0.72 mg/kg and in kidney 0.34, 1.1 and 4.9 mg/kg. Residues in milk were 0.37, 1.0 and 6.0 mg/kg (mean for day 7-28), but results above 0.6 mg/kg lindane in milk are considered invalid because of bad procedural recoveries (48%-142%).

Hampshire cross-bred feeder lambs (one male and one female per group) were dosed orally with lindane at levels equivalent to 17.5, 52.5 and 175 ppm in the feed for 28 days as before and slaughtered 10-12 h after the last dosing. No difference between residues in male and female lambs was observed, so results are given as the mean for each group. Results below 0.2 mg/kg are considered invalid because of matrix interferences in control samples. Residues in fat were 19, 43 and 198 mg/kg for the 17.5, 52.5 and 175 ppm lambs respectively. Residues in muscle were 0.73, 1.6 and 7.7 mg/kg, in liver 0.02, 0.02, and 0.12 mg/kg and in kidney 0.74, 1.8 and 4.8 mg/kg.

Yorkshire/Landrace cross-bred pigs (one male and one female per group) were dosed orally with lindane at levels equivalent to 7.0, 21 and 70 ppm in the feed for 28 days as before and slaughtered 6-10 hrs after the last dosing. No difference between residues in males and females was observed, so results are given as the mean for each group. Residues in fat were 1.7, 5.6 and 16 mg/kg, in muscle 0.086, 0.24 and 0.78 mg/kg, in liver <0.02, <0.02, and <0.02 mg/kg and in kidney 0.049, 0.21 and 0.39 mg/kg.

Leghorn laying hens (four birds per group) were dosed orally by gelatin capsule with lindane at levels equivalent to 1.5, 4.5 and 15 ppm in the feed for 28 or 60 days after the morning egg collection (two groups of 4 hens at each level for each period). Eggs from days 0, 1, 3, 7, 14, 21, 25, 28, 35, 42, 49, 56 and 60 were analysed. Birds were killed 20 h after the last dosing. Samples were composited by group. Residues were similar in the four groups at each dose level. Mean residues in fat were 2.5, 8.3 and 28 mg/kg for the 1.5, 4.5 and 15 ppm hens respectively. Mean residues in thigh muscle were 0.18, 0.44 and 1.4 mg/kg, in breast muscle 0.03, 0.09 and 0.35 mg/kg, in liver 0.11, 0.38 and 0.84 mg/kg, and in kidney 0.18, 0.49 and 2.0 mg/kg. The highest individual residues at 1.5, 4.5 and 15 ppm were 2.7 mg/kg, 9.7 mg/kg and 29 mg/kg in fat, 0.19 mg/kg, 0.60 mg/kg and 1.6 mg/kg in thigh muscle, 0.04 mg/kg, 0.12 mg/kg and 0.40 mg/kg in breast muscle, 0.21 mg/kg, 0.71 mg/kg and 2.5 mg/kg in kidney, and 0.14 mg/kg, 0.55 mg/kg and 0.95 mg/kg in liver. The mean residues in eggs were 0.21, 0.59 and 2.2 mg/kg, and the highest residues in individual group composites were 0.35, 0.68 and 2.6 mg/kg at the three dose levels.

Residues in animal commodities

The estimated maximum dietary burdens for beef and dairy cattle were 0.05 and 0.1 mg/kg feed respectively, so the dairy cattle burden represents the worst case. In the feeding study with dairy cows, the lowest dosing level was 20 mg ai/kg feed. The resulting residues in tissues and milk were calculated by applying the transfer factors at this level to the dietary burdens. (Transfer factor = residue level in sample ÷ feeding level). The dietary burden for poultry was 0.009 ppm, which was lower than the lowest feeding level in the feeding study (1.5 ppm) so, the resulting residues in eggs and poultry tissues were calculated by applying the appropriate transfer factors at this feeding level. Residues in pork commodities were similarly calculated from the lowest level fed in the pig feeding study (7 ppm).

The highest individual residues in tissues and eggs from the lowest levels fed in the feeding studies were used in conjunction with the maximum dietary burdens to calculate the highest likely residue levels, and in conjunction with the STMR dietary burdens, to estimate the STMRs, in commodities derived from cattle, poultry and pigs.

Calculation of MRLs and STMRs for animal tissues

¹ Values in italics are the estimated dietary burdens. Values in normal font are the lowest feeding levels in feeding studies.

² Residue values in parentheses in italics are extrapolated to the dietary burdens from the lowest feeding levels used in the feeding studies and the residues found in those studies.

³ Mean (in roman) is the mean tissue or milk residue in the relevant feeding group.

⁴ High (in roman) is the highest individual animal tissue residue in the relevant feeding group.

The Meeting estimated maximum residue levels of 0.1 mg/kg (fat) for meat from mammals other than marine mammals, 0.01* mg/kg for edible offal and 0.01* mg/kg for milks, and STMRs of 0.0007 mg/kg and 0.008 mg/kg in muscle and fat from mammals other than marine mammals respectively, 0.0002 mg/kg for edible offal and 0.0003 for milks, and HRs of 0.005 mg/kg and 0.06 mg/kg in muscle and fat from mammals other than marine mammals respectively, and 0.002 mg/kg for edible offal.

CXLs exist for eggs (0.1 mg/kg E) and poultry meat (0.7 mg/kg (fat) E). These recommendations stem from 1968/1969 and 1973, when maximum residue levels for animal commodities were defined as EMRLs. Currently, this designation is reserved for pesticide residues arising from environmental sources other than the use directly or indirectly on the commodity.

The Meeting recommended MRLs of 0.05 mg/kg for lindane in poultry meat (fat), 0.01* mg/kg in edible offal of poultry and 0.01* mg/kg in eggs to replace the current CXLs of 0.1 mg/kg E for eggs and 0.7 mg/kg (fat) E for poultry meat, and estimated STMRs of 0.0006 mg/kg and 0.008 mg/kg for poultry muscle and fat, 0.0004 mg/kg in edible offal of poultry and 0.0007 mg/kg in eggs, and HRs of 0.001 mg/kg and 0.016 mg/kg in poultry muscle and fat, 0.001 mg/kg in edible offal of poultry and 0.002 mg/kg in eggs.

DIETARY RISK ASSESSMENT

Long-term intake

The International Estimated Daily Intakes of lindane, based on the STMRs estimated for 13 commodities, for the five GEMS/Food regional diets were in the range of 0 to 1% of the maximum ADI of 0.005 mg/kg bw (Annex 3). The Meeting concluded that the long-term intake of residues of lindane resulting from its uses that have been considered by the JMPR is unlikely to present a public health concern.

Short-term intake

The International Estimated Short Term Intake (IESTI) for lindane was calculated for 13 food commodities for which maximum residue levels were estimated and for which consumption data were available. The results are shown in Annex 4.

The IESTI represented 0% of the acute RfD for the general population and 0% of the acute RfD for children. The Meeting concluded that the short-term intake of residues of lindane resulting from its uses that have been considered by the JMPR is unlikely to present a public health concern.