Chlorinated hydrocarbons in beef , cow liver and milk products and total mercury in cow liver

The chlorinated hydrocarbons used in pesticides and PCB-compounds (polychlorinated biphenyls) were determined in domestic and imported beef (79 samples), cow liver (195 samples), butter (112 samples), cheese (93 samples) and milk powder (58 samples); mercury was determined in cow liver (163 samples). The domestic samples (320 samples in total) were collected from different parts of F'inland. The foreign samples (270 samples in total) came mainly from the Nordic countries and Central Europe. The chlorinated hydrocarbons were determined by gas chromatography with an E.C. detector. The mercury determinations were made from freezedried samples using a Coleman Analyzer. In the domestic samples the contents of chlorinated hydrocarbons were low and clearly below the FAO/WHO recommended limits. The pesticide quantities in the foreign samples were often higher, and in two cases the total DDT limit recommended by FAO/WHO was exceeded. The mercury contents of the livers were low and of the same magnitude in all samples examined.


Introduction
The use of pesticides has been limited by law in Finland; the use of mercury has been controlled since the middle of the 1960's and that of chlorinated hydrocarbons since the beginning of the 1970'5.
However, since the decomposition of many organic compounds in nature is slow, they may accu- mulate in animals and through them enter into food.A corresponding ten- dency has been observed concerning many metals which in sufficiently high concentrations in food may be detrimental to human health.In addition to domestic products, fairly large quantities of imported foodstuffs are used, and our knowledge of their contents of harmful compounds is limited.Thus contin- ued research and control in this field is required.
This study deals with domestic and imported beef and cow liver, which is an important imported raw material for the meat industry.As a second group, milk products (butter, cheese and milk powder), which have a large domestic consumption, have been chosen; in addition they are important export articles.Analyses of chlorinated hydrocarbons, including polychlorinated biphenyls (PCB) were taken from all samples.Total mercury determinations were made in cow liver.

Material
Domestic beef and cow liver were obtained from five different slaughterhouses in Southern and Central Finland.Foreign beef and liver samples were obtained in connection with customs clearance of food lots coming from different countries (Table 1).
Butter, cheese and milk powder samples were obtained from dairies operating in different parts of Finland.Foreign milk products were random purchases mainly from other Nordic countries where similar studies have been made.
The rest of the material consisted of occasional samples from Central and Southern Europe and the U.S.A. (Table 1).

Chlorinated hydrocarbons Extraction and cleanup
The fresh sample (beef 10 grams, cow liver 5 grams, butter 1 gram, cheese 2 10 grams, milk powder 4-50 grams) was homogenized with anhydrous sodium sulphate.The homogenate was then shaken in a flask with a glass plug with diethyl ether (25 to 100 ml) about 3 minutes and the extract was filtered through glass wool.The ether was evaporated at room temperature.
The fat was dissolved in 5 ml of hexane and decanted into a separatory funnel (250 ml) and rinsed with 3 X 3 ml of hexane.Fifteen milliliters of acetonitrile saturated with hexane were added and shaken vigorously for I-2 minutes.After the layers had separated the acetonitrile was drained into a 150 ml glass bowl.The shaking was repeated with three 15 ml portions of acetonitrile.The acetonitrile extract was evaporated at 60-70°C by blowing purified nitrogen slowly down into the glass bowl.Methylene chloride was added in a sufficient amount and the fat in the methylene chloride solution was then applied on b thin layer plate.The thin layer plates (50 X 200 mm) were covered with Silica Gel G so that the layer was 1 mm thick (Shandon Equipment for Thinlayer Chromatography) (Karppanen et ai. 1969).The solvent fronts, the border line between the upper and lower section and the origin line were marked on the plates, which were then heated overnight at 200°C.The plates with fat on the origin line were developed with the solvent methylene chloride and n-hexane, 25: 75 (v/v).After drying at 25°C both the upper and the lower sections of the thin layer material were removed and packed into small glass columns.They were then extracted with cyclohexane and diethyl ether, 6: 4 (v/v).The eluates were collected in 1 ml flasks.The solution from the upper section contained PCB compounds, p.p'DDE and p.p'DDT.To separate p.p'DDT and a major PCB peak 0.5 ml of the eluate was treated with a methanol solution of 10 per cent KOH (w/w) Gas chromatography Gas chromatograph: Varian 600 and (tritium) and glass columns.

Calculation of PCB
After the pesticide residues from the sample had been removed, the sum of the heights of all peaks corresponding to PCB peaks was calculated with the exception of the two interfering with p.p'DDE.This sum was compared with the sum obtained from the same peaks in the reference chromatograms.
By using the method of acetonitrile partition (Zweig and Sherma 1972)   it has been shown that both pesticides and PCB decrease.Average recovery of pesticides is 95 % and that of PCB 70 %.Organochlorine compounds may decrease during evaporation of acetonitrile.

Results and discussion
In the result tables only those chlorinated hydrocarbons detected in the samples are shown.The sum of DDT compounds was calculated and mentioned in the tables as total DDT.
Dieldrin was found in small quantities only in the Polish liver samples (Table 2).However, parts of the liver samples have been cleaned by the H 2 S0 4 -method (Ahling and Jensen 1970), during which the dieldrin dissolves and cannot be detected.The highest total DDT value was also detected in Polish liver.If the results are compared to the suggested FAO/WHO limit of 7 mg/kg fat (Anon. 1973), one Polish liver sample exceeded this value.In the domestic liver samples the total DDT content was low.In one of the domestic samples an abnormally high PCB content was found.The sample was from a cow which during the grazing period had been drinking water from the Kokemäki river; this river belongs to the Finnish water system most seriously polluted by PCB compounds.The mercury contents of the livers were low and of the same magnitude in the different countries.The highest values were found in liver imported from the U.S.A., but the limited material does not justify definite conclusions.
In the Finnish and Irish beef samples examined, only small residues of DDT decomposition products were found (Table 3).On the other hand, the average total DDT in the Polish beef samples examined was considerably higher, exceeding in one sample the FAO/WHO recommended limit of 7 mg/ kg fat (Anon. 1973).Small amounts of PCB were found in Finnish beef samples only.
In the Finnish, Swedish, Danish and Irish butter samples analysed, the contents of chlorinated hydrocarbons were of the same magnitude and fairly low (Table 4).Results in agreement with this study have also been obtained in Sweden (Westöö et al. 1970), Denmark (Bro-Rasmussen et al. 1968) and   Ireland (Downey 1972).The Danes, however, have recorded considerable BHC-values (/TBHC and lindane), whereas the 13 Danish butter samples in  our material did not contain detectable amounts of these compounds.This may depend on differences in the methodology.
There were no significant differences in the average residue contents of the Finnish and Danish cheese samples (Table 5).However, there was in the Danish samples some heptachlorepoxide, which was not found in the Finnish samples.In the cheese samples originating from other countries (France, Germany) clearly higher amounts of dieldrin and DDT were found than in samples from the Nordic countries.
All the examined milk powder samples contained only small residues of chlorinated hydrocarbons (Table 6).
Table 5. Organo chlorine content in cheese.Mean concentration, mg/kg fresh sample. (Range in parentheses).

Country Number Lindane
Heptachlor-

Table
. The samples from the various countries.

Table 2 .
Organo chlorine content and total mercury in cow liver.Mean concentration, mg/ kg fresh sample. (Range in parentheses)

Table 3 ,
Organo chlorine content in beef.Mean concentration, mg/kg fresh sample. (Range in parentheses).

Table 4 .
Organo chlorine content in butter.Mean concentration, mg/kg.Range in parentheses.