7. RESULTS OF SUBSYSTEM 4: HEALTH CONSEQUENCES AND RISKS OF HUMAN DIETARY EXPOSURE TO CHEMICALS |
7.1 Organization of the monitoring activities
The subsystem is composed of two parts and is carried out in twelve cities (Tab. 3.1). This number was optimized in order to obtain statistically representative results. The first part of the subsystem is aimed at the notification of foodborne infectious diseases (alimentary infections and cases of intoxication). It utilizes the data collected in the epidemiological system EPIDAT and those available in reports of Public Health Service. The second part is focused on the monitoring of dietary exposure of the population to selected contaminants. Samples of foodstuffs selected for determining exposure are collected at a center (accredited by the Czech Accreditation Institute) to be culinarily processed and analyzed according to the standard procedure. This allows the obtaining of comparable and high quality analytical results.
7.2 Incidence of alimentary infections and intoxications
Alimentary infections and intoxications form a group of infections that, upon ingestion of contaminated food, mainly affect the gastrointestinal tract of humans. Their incidence rate has been followed up since 1993 and their analysis is first of all focused on important etiological agents (Salmonella spp., Shigella spp., Citrobacter spp., Escherichia coli, Yersinia enterocolitica, Staphylococcus aureus, Clostridium perfringens, rotaviruses, adenoviruses, coronaviruses and the type A hepatis virus), as well as on the comparison with data for the population of the Czech Republic.
There occurred a change in the epidemiological situation concerning salmonellosis in the Czech Republic in 1998. After a two-year general decrease in the incidence rate of this affection in the years 1996 and 1997, there again came about an increase in reported morbidity. 50 791 cases of salmonellosis (493 per 100 000 of the population) were registered, roughly corresponding to the incidence rate in 1994. An increase was detected in all the regions except for a single one (Plzeň) where to the contrary there occurred a drop in morbidity from 594 to 350 cases per 100 000 of the population (Fig. 7.1a). The number of deaths due to salmonellosis (30) rose by 14 in 1998 in comparison with the previous year: two died of salmonella sepsis and 27 in the acute stage of the illness; also one carrier of a salmonella strain died. The major etiological agent continues to be S. enteritidis phage type PT 8. There was a newly detected phage type PT 2 (protracted epidemic occurrence in Hradec Králové and Benešov). In 1998 it was found that S. typhimurium (STM) did not yet spread in the Czech Republic and in selected localities as much as in neighboring countries. Its share in the epidemiology of salmonellosis was 1.9% and was lower in 1997. Nevertheless, in 1998 in the district of Hodonín (not a part of this subsystem of monitoring) the first epidemic caused by the multiresistant STM DT 104 was registered. The other epidemiological data (distribution of cases by age, genders, seasonality, pathways of transmission and suspect vehicles) remained unchanged in 1998. In some localities (České Budějovice, Jablonec, Plzeň and Šumperk) anamnestic data on suspect vehicles were lacking just as in previous years. In the year 1998, 48 epidemic occurrences of salmonellosis was reported in the regions under follow-up. Hitherto, it was the greatest number over the period under follow-up since 1993. One of the epidemics was nosocomial (63 cases at the University Hospital in Prague, the vehicle being puréed meat positive for SE PT 8).
Campylobacteriosis were the second most frequent alimentary infection of bacterial origin. Morbidity has an ever increasing trend (Fig. 7.1b). In 1998 5 542 cases of campylobacteriosis (54 per 100 thousand of the population) were reported in the Czech Republic. An increase was apparent in all the localities except for Žďár n/S where there was a moderate decrease (in that locality the annual incidence rate was among the highest). On the contrary there has not been reported a single case of campylobacteriosis in Jablonec n/N, this situation repeating itself since 1993.
Shigellosis morbidity has an ever declining trend. In 1998 511 cases were reported in the Czech Republic (i.e. 5 per 100 000), that being the lowest annual incidence rate registered. A decline was found in all the localities under follow-up except for Prague where there was a moderate increase (the greatest number being in the age group of 20 - 34 years).
The occurrence of infections caused by E. coli decreased by 145 cases in 1998 as against 1997. Morbidity due to this infection was the lowest in the past three years. Serovar OO1577 causing hemorrhagic enteritis or the HUS syndrome in small children, was detected in 126 cases, that being 29 isolations more than in 1997.
The epidemiological situation in yersiniosis has not changed. In 1998 there were reported 159 cases of the disease, at approximately the same level as in the previous year (155). The only etiological agent was Y. enterocolitica. The problem of yersiniosis is studied predominantly at the Regional Public Health Center in Ostrava.
The incidence rate of alimentary intoxications in 1998 was higher by 165 cases as against the previous year. The number of regions that followed up and reported this affection was low, however. A greater number of cases was reported in Žďár n/S. In question was an epidemic occurrence (63 people were affected, the vehicle being risotto).
Laboratory diagnostics of alimentary infections caused by viral agents is demanding and depends on the technical equipment of the laboratory, and therefore it is not utterly routine. The problem of rotaviruses (239 cases of rotavirus infection were reported in the Czech Republic) is traditionally taken up by Prague, Plzeň and České Budějovice that of adenoviruses by Prague and Plzeň; and that of intestinal infections caused by Norwalk virus and coronaviruses, by Prague only. In 1998 there was a decline in reported cases of hepatitis type A in the Czech republic, from 1195 cases in 1997 down to 904 in 1998. A decline was registered in Prague, Brno and České Budějovice; a rise in Jablonec and Šumperk. Benešov and Znojmo did not report a single case of VHA. The Romany gypsy population represented 7.4% of all cases while in 1997 it was 13.7%.
7.3 Dietary exposure of humans
The major objective of monitoring is the estimate of the mean value of exposure to chemical substances (important contaminants of foodstuffs or nutrients and micronutrients). Their content in foodstuffs influences the health risk of tumor and non-tumor diseases. The result of monitoring is therefore foremost the assessing of the health risk in the population of the Czech Republic.
In the year 1998 there was for the first time also followed up by orientation the iodine content in the foodstuff consumer basket as a contribution to the effort of resolving its insufficient intake that is being found in the Czech population. Besides that, 55 other individual chemical substances were followed up.
The implementation of the program of monitoring is based on a standard organizational pattern. The consumer basket (Fig. 7.2) under follow-up was made up of 160 basic kinds of foodstuffs. That was secured in the course of the year by purchases in the commercial network. Overall, 1 920 samples of foodstuffs were analyzed, that were, for economizing reasons, combined into 552 so-called composite samples for chemical analyses. For analysis of calcium, phosphorus, sodium, potassium, magnesium, nickel, chromium, aluminium, iron, iodine and total arsenic the food samples were also combined into 46 so-called representative composite samples (joining analogous type samples (46 types) from all 12 sampling sites into one sample). These were also used for the analysis of so-called toxic isomers of PCB. Prior to their chemical analysis the foodstuffs were culinarily treated in a standard way (cooked, baked, peeled, washed, etc.) and then mixed into composite samples that were analyzed after their homogenization into the form of laboratory samples. Exposure was calculated on the basis of analytical results and knowledge of the standard food consumption pattern of an average person in the Czech Republic. On the basis of the results obtained one can formulate the following conclusions for the management of health risks.
In 1998 the mean chronic exposure of the population to the organic substances under monitoring (polychlorinated biphenyls (PCBs), aldrin, endrin, dieldrin, methoxychlorine, endosulphane, heptachloroepoxide, hexachlorobenzene (HCB), alpha-, beta-, delta-, gamma- (lindane) isomers of hexachlorocyclohexane, isomers of DDT, DDD, DDE) from foodstuffs did not reach critical values (Fig. 7.3a) which are connected with an unacceptable increase in the probability of damage to the consumer’s health (in their non-carcinogenic effect). The largest numbers of findings (above the limit for determination) were again observed for p,p-DDE (52%), PCB congeners 153, 138 and 180 (50, 46 and 43% respectively) and HCB (39%). That is evidence of vast indiscriminate contamination, albeit at low concentration levels. In the other substances the frequency of positive samples was low (more than 15% but less than 50%) or even nil, and therefore such contaminants are not the subject of quantitative evaluation.
The mean chronic exposure to inorganic substances (nitrates, nitrites, cadmium, lead, mercury, arsenic, copper, zinc, manganese, selenium, magnesium, chromium, nickel, aluminium, iron and iodine) did not exceed exposure limits for a non-carcinogenic effect (Fig. 7.3b). Exposure to nitrates continues (27 - 43% of the ADI, the meaning of the individual exposure limits is described separately in the chapter eleven of this report) as well as to nitrites (25 - 37% ADI). The intake of manganese is stable (45 - 55% RfD). Exposure to cadmium has again increased moderately (23 - 36 PTWI) and surprisingly that of lead (11 - 17% PTWI) is also increasing moderately. In the past five years exposure to mercury has reached benign values (1 - 2% PTWI). The intake of copper and zinc has remained low (4 - 5% and 19 - 22% PMTDI, respectively). Exposure to arsenic did not decrease further and remained at the same level (4 - 6% PTWI) while a persisting moderate increase in selenium intake (14 - 19% RfD) was observed. Estimate of the exposure values for nickel and chromium reached relatively low and stable values (9% and 12% RfD, respectively). Likewise, estimates for aluminium and iron did not present any risk of damage to health in consumers (5% PTWI and 25% PMTDI, respectively).
The distribution of exposure to three significant contaminants, to the sum of PCBs, arsenic and selenium in the individual cities is illustrated in Fig. 7.3c, 7.3d, 7.3e. Exposure to PCB (Fig. 7.3c) is similar in the individual cities (except for Ostrava where a relatively wide range of values over the years of the monitoring was found). Data for arsenic are presented in Fig. 7.3d for the so-called “toxic” arsenic (sum of inorganic compounds and it methylated forms: methyl- and dimethylarsenate). The exposure limit is related to this so-called “toxic” arsenic and the revealed exposure represents, as has been mentioned, 4 - 6% of the exposure limit. The values of exposure to selenium (Fig. 7.3e) in the individual cities are likewise similar, in none of them does there occur any extreme burden.
In the assessment of trends of exposure to individual pollutants over the period of 1994 through 1998 there was taken into consideration only such substances in the analysis of which at least 50% of the values were above the limit for determination. This condition was met by: nitrites, nitrates, zinc, copper, manganese, selenium, lead, cadmium, mercury, arsenic, p,p-DDE and PCB 153. From the results of statistical processing it follows that the hypothesis of random distribution of exposure values over the period of five years cannot be refuted. That means that the values found vacillate randomly around the mean value without any positive or negative temporal correlation.
For the evaluation of the intake (Fig. 7.4) of certain trace elements (zinc, copper, selenium, chromium, nickel, manganese, magnesium, calcium, phosphorus, sodium, potassium, iron), exposure was determined which for zinc vacillated around 82% of the recommended population intake. In copper they were only moderately below the normative minimum (92%). Selenium intake was at the level of the normative minimum (115%) for the population (it is positive information). The estimate of the normative minimum for chromium was covered at 107%. The contemplated requirement for nickel was covered at 306%, that of manganese at 127%, magnesium at only 75%, calcium at 95% and phosphorus at 189%. The upper limit for sodium intake reached 88% (i.e. 152% of the N.A.S. USA recommendation) and the requirement for potassium was covered at 100%. The intake ratio of Ca/P was repeatedly relatively low, on the other hand that of Na/K was relatively high. Iron intake reached 90% of the recommended level for population.
A theoretical estimate of the probability of an increase in the numbers of tumor affections in our population (Fig. 7.5) due to exposure to selected chemicals (sum of PCBs, alpha- and beta- isomers of HCH, lindane, p,p- isomers of DDT, DDD and DDE, aldrin, dieldrin, heptachloroepoxide, HCB and arsenic) made up about 133 - 198 additional cases in the Czech Republic in 1998. Traditionally it were PCBs, As and HCB that represented the greatest share in the increase of this risk.
7.4 Partial conclusions
Results of the subsystem in 1998 indicate a moderate decrease in exposure to certain dangerous chemicals in the Czech Republic. The dietary exposure of humans to chemical substances shows favorable signs of decrease in exposure to pesticides based on chlorinated hydrocarbons; however, the undesirable exposure to PCBs persists and even increased somewhat in 1998. Undesirable is the persisting exposure to certain toxic metals. Comforting is a rise in the intake of selenium, and a decline in that of toxic arsenic. The intake of certain trace elements is at the level of the basal or normative minimum (Cu, Zn). The intake of basic nutrients (Ca, P, Na, K, etc.) cannot be said to be optimal from the point of view of the expected impact on consumer health. Iodine intake through the use of iodized salt for preparing meals suffices to cover the mean dose recommended for our population and that confirms the presumption that iodized salt is the major widely available means for overcoming iodine deficiency in our population.