RU2316260C2 - Method for evaluating the risk in the development of iodine-deficient state in population of administrative region under conditions of anthropotechnogenic chemical environmental pollution - Google Patents

Abstract

FIELD: medicine, ecology.

SUBSTANCE: the present innovation deals with systemic ecologo-hygienic evaluation of the degree of medico-ecological situation. One should detect the value of environmental pollution for each chemical element being harmful for every age health group (P_x). For each region of the tested area it is important to detect the sickness rate of thyroid gland (TG) associated with iodine-deficient state (IDS). The sickness rate should be established for different age groups and based upon the detected sickness rate it is possible to determine the chance for the development of IDS (D_x). Based upon the obtained IDS-associated TG-sickness rate one should conclude upon nosologic forms of the disease in question. It is necessary to determine the risk in the development of different nosologic forms of IDS-associated TG-diseases according to the following formula: R_x=P_xD_x, where x - any chemical ecotoxicant. Moreover, it is necessary to plot the obtained risks onto the region map that illustrates the sickness rate in the region in question. Based upon the obtained date one should predict the risk in the development of IDS. The innovation enables to evaluate real and potential risks in the development of IDS at higher degree of probability and the onset of IDS-associated TG-diseases under conditions of anthropotechnogenic chemical environmental pollution.

EFFECT: higher efficiency and accuracy of evaluation.

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Description

The invention relates to medicine and ecology and can be used for systemic ecological and hygienic assessment of the degree of tension of the medical and environmental situation for the purpose of subsequent planning and implementation of a set of preventive and therapeutic measures.

The relevance of the invention is due to the need to develop new hygienic technologies for a comprehensive assessment of the potential and real health risks at the population level.

As a prototype, a well-known method of hygienic diagnosis and assessment of the tension of iodine deficiency states (IDS) in the territory with the combined impact of environmental factors (patent No. 2206272, priority 2001.12.05) was selected. The specified prototype method is the closest to the claimed invention. It is based on the diagnosis of iodine deficiency in the population under conditions of chemical pollution of the territory according to clinical and biochemical parameters. Based on the allocation of priority chemical pollutants in the known method, mapping of IDS tension in a given territory is carried out, and priority indicators of IDS are selected. Based on the data obtained, a territorial monitoring, prevention and correction program for IDS in the study area is being formed. The analysis of the given examples shows the influence of chemical environmental ecotoxicants (OS) on the occurrence and spread of IDS in the population of the studied territory (Perm region). However, the approaches used in the prototype method to the sanitary-hygienic assessment of the danger of chemical pollution of OS facilities, the determination of the real and permissible human load of chemicals and the development of environmental assessment criteria mainly provide for a qualitative assessment of the load hazard of adverse factors in the occurrence of IDS in the population. This circumstance limits the possibilities for the applied use of the known method and system of such an assessment for managing the health of the population of the study area, the development and implementation of specific systems for the integrated assessment of the multiple combinations of various adverse environmental factors in the development of IDS among the population, taking into account the totality of the factors of the integral impact in the “environment” system -health of the population ”in the administrative territory. As a basis for the territorial program of monitoring, correction and prevention of IDS in the study area, the prototype method proposes a scheme for assessing the harmful load on the environment and predicting the development of IDS in the population, as well as the real load of adverse OS factors on public health, taking into account the total clinical and biochemical parameters . However, the proposed methodological approaches do not provide for the establishment of a relationship between the identified real chemical load and changes in the health of the population, in particular, the functional state of the thyroid system.

At the same time, the current level of sanitary and environmental expertise provides for the use of an integrated approach to assess the tension of the medical and environmental situation and the real risk to human health, taking into account the analysis of causal relationships of the harmful load on the environment and specific changes in the health of the population. In this case, a method is needed for an integrated assessment of the potential and real risk of developing IDS in the population and the danger of an imbalance in the balance of chemicals (environmental pollution by environmental toxicants) on the living environment of the population of the study area.

There is also a method for the early diagnosis of thyroid dysfunction (thyroid gland) in children by mathematical analysis of a number of risk factors (reg. Application No. 2002216464/14, priority from 2002.07.29), characterized in that an integrated assessment of the risk of thyroid dysfunction (Q) is performed by the formula

where Ni is the absence of an informative feature;

Oi - the presence of an informative sign;

Ri is an expert assessment of confidence in the i-th informative attribute,

and with a Q value greater than 26.5, thyroid dysfunction is diagnosed. The known method is based on the use of integral estimation. The analysis of the examples cited by the authors did not reveal the mechanisms that ensure the application of the method when assessing the medical and environmental problems of the territory. In addition, the authors do not take into account the morphological changes in the thyroid gland (increase in volume, change in structure, echogenicity) that often precede functional disorders and are compensatory in the proposed integral assessment formula.

There is also a method of assessing the risk of cardiovascular diseases and other disorders, including thyroid diseases (reg. Application No. 99101946/14, priority from 1996.07.03). In the known method, the risk assessment of thyroid diseases is carried out on the basis of a comparison of the ratio in the blood of the content of phytosterol and total cholesterol in a healthy control and studied individuals. However, in the known method, the relationship between the risk of thyroid disease and adverse OS factors is not investigated, which excludes the possibility of risk management, i.e. the possibility of its reduction by eliminating or reducing the factor impact of the habitat. The proposed method can be considered, rather, as a marker of premorbid diagnosis of cardiovascular diseases and other disorders, including thyroid diseases, and not as a way of assessing the integral impact in the system "environment - public health" in settlements and regions.

The claimed invention is aimed at solving the problem of assessing the real and potential risk of developing iodine deficiency in the population of an administrative territory under the conditions of anthropogenic chemical environmental pollution, taking into account the analysis of cause and effect relationships. Using for practical purposes the proposed method allows to achieve several technical results:

- a methodology has been proposed for integrated assessment of the real and potential risk of the influence of a harmful chemical factor (toxicants in CO), taking into account its multicomponent nature and variability as the most often realized risk to human health, in particular the development of IDS;

- the use of an integrated assessment of multiple combinations of various chemical factors for the analysis of cause-effect relationships in the system "human health - environment";

- development of a conceptual model for the study of IDS in the administrative territory;

- characterization of the influence of the medical and environmental situation of the territory with anthropogenic chemical pollution on the functional and morphological parameters of the thyroid system.

These technical results in the implementation of the claimed invention are achieved due to the fact that, as in the prototype method, the environmental and hygienic assessment of the OS of the study area is carried out through the study of the distribution and severity of IDS as an environmentally caused pathology, i.e. a state that is etiologically and pathogenetically related to the ecological state of the territory (region) and is formed under the influence of natural or anthropogenic harmful factors. A feature of the proposed method lies in the fact that the determination of the tension of the medical and environmental situation in the region is carried out by analyzing the cause-effect relationships between the quantitative and qualitative characteristics of harmful factors and the reaction of the human body (development of IDS). The essence of the invention is an ecological and hygienic assessment of the quality of the environment in connection with the exposure to the human body of chemical factors of environmental objects, a ranking assessment of the factors according to the degree of their potential danger, the real and potential risk of developing IDS.

SUMMARY OF THE INVENTION

The main provisions of systematic environmental analysis, formulated in the 80s of the last century, served as the basis for numerous studies on a comprehensive assessment of the impact of adverse environmental factors on public health. Adverse OS factors in large industrial centers and regions of the country form a certain morbidity structure specific to a given administrative territory.

The mechanism of the body's reaction to various changes in the external environment is universal in nature, which causes certain difficulties when trying to establish the causes of the occurrence of environmentally caused pathology in each case. However, a comparative analysis of the incidence of the region’s population allows us to determine the list of diseases characteristic of the study area.

The quality of life and the adaptation of the organism to the parameters of the living environment largely depend on the functional state of the neuroendocrine system, the most important link of which is the thyroid gland.

The tense ecological situation prevailing in a number of regions of the country caused the growth of morbidity indicators in the population. In most regions, an increase in thyroid pathologies associated with iodine deficiency was noted [2, 7, 12, 13].

Studies conducted in recent years prove that in most of Russia there is a low iodine content. However, the results of the studies showed that IDS also develops in areas relatively prosperous in natural iodine content in OS facilities. An example of this is the Far Eastern regions, the northern regions of Siberia and the Urals. The term “relative iodine deficiency” appeared, due to the influence of adverse environmental factors (usually of a chemical nature) on the thyroid system, creating conditions for the disruption of normal iodine metabolism in the body.

The results of numerous studies on the cause-effect relationships of the spread of thyroid diseases associated with iodine deficiency and adverse environmental factors, conducted in a number of regions of the Russian Federation, made it possible to classify IDS as an indicator of environmentally caused pathology.

Hence the main feature of the claimed invention is the risk assessment of the development of IDS as a marker of the ecological disadvantage of the administrative territory.

The method is carried out in the following way.

Adapting numerous definitions of the concept of “risk” to the claimed invention, the risk of developing an iodine deficiency state of the body should be considered as the probability of developing IDS in the population of a given territory in a certain period of time. Any risk can be considered as a derivative of the likelihood of unwanted exposure and harm to health. In a general sense, for a specific chemical ecotoxicant, the risk of developing IDS can be represented in the form of a formula:

where x is any chemical ecotoxicant; P _x is the probability of OS contamination and the effect on the human body; D _x - the likelihood of developing IDS.

The administrative territories of the Primorsky Territory and the data of medical statistics on the incidence of thyroid gland associated with iodine deficiency among the population of the Territory are taken as a model and example for calculating the risks of developing IDS.

Modeling the risk of disease by primary thyroid morbidity associated with iodine deficiency

To model the statistical relationship between thyroid incidence and ME content in the soils of Primorsky Krai, a standard modeling scheme was used for the class of binary selection models.

Using the logit model as one of the methods for modeling dichotomous features

we obtain the observation equation:

where r (θ'H _k ) is the probability of thyroid disease under the given geochemical conditions H, the value of ε _k indicates the experimental error, presumably with zero mathematical expectation and the final dispersion, and r _k is the amount of thyroid incidence in this area in this age group.

Actually (3) represents the relative frequency of complaints of residents of a certain age in a given region (administrative territory) regarding thyroid diseases associated with IDS.

Suppose that the j-th resident of the k-th administrative territory received thyroid disease during the year, then the value of y ^(k) _j is equal to one and equal to zero if this resident of this territory did not get this nosology. Then

Under the assumptions under consideration, the quantity r _k is a binomial random variable. To reconcile formulas (3) and (4), it is necessary that

where R _k = P {y ^(k) _j = 1 | H _k }.

It follows from (5) that experimental errors are associated with observations (4), in which the variances depend on k, i.e. from the value explaining the variable.

The optimal values of the model parameters from the minimum requirement of the criterion of the generalized least squares method are determined by the following formula:

When introducing new variables to simplify the assessment

уравнение наблюдения (6) принимает вид:

observation equation (6) takes the form:

Where

Observation equation (8) corresponds to a linear model. The minimized criterion (7) should be replaced by the function

The solution of the optimized problem (9) allows us to determine the model (5), estimate the risk value r at points with unknown parameter values (OS N), and proceed to the actual mapping of the territory of the Primorsky Territory.

Modeling the risk of thyroid diseases associated with IDS according to the total incidence of the region’s population

To model the risk of thyroid morbidity for a specific age group, the following method was used.

The vectors of aggregated geochemical indices (concentration of cholesterol in the soils of the region's regions) act as explanatory factors, and the risks of thyroid disease for the population of the region of different age groups are the explained variable. Using statistics on the general incidence of thyroid gland, we used the Poisson mathematical model.

The main condition that determines the regression Poisson model is the assumption about the form of the distribution of the random variable Y:

where Y is the number of appeals of one randomly selected resident of any administrative formation of the region regarding a specific thyroid disease. The variable Y is a random variable whose distribution depends on the state of the environment N.

The generally accepted assumption that the distribution parameter is non-negative is the exponential dependence

Let y ^s _j be the value of Y for the jth resident of the sth region of the region. By virtue of (10) and (11):

In fact, the values of the variables y ^(s) _{j are} unknown and are auxiliary in nature. Really observed average

Thus, the observation equation can be represented as

where ε _k is the value of the centered random variable and, by virtue of (11):

The risk of developing IDS in the population of a given region r _s is the probability that a resident of this area will apply for this nosology at least once during the year. Then

The values of the model parameters are determined according to the criterion of the generalized least squares method

Algorithmic modeling is reduced to solving the extremum problem (17). The calculation, by virtue of this requirement, of an estimate of the parameters Θ allows us to evaluate the risk values.

To calculate the relative risk of IDS in the population of the study area, the formula is used

where R _about - the relative risk of developing IDS in the population; R _in - the risk of development in a population exposed to a chemical factor; R _k - the risk of development in a population not exposed to a chemical factor.

Building a map of the risks of developing IDS among the population of the region

Based on the mathematical models outlined, administrative territory is mapped. At the first stage, geochemical data on the content of chemical elements in the OS objects are averaged, normalized to background concentrations, and aggregated to administrative regions. Medical data on thyroid diseases associated with iodine deficiency for different age groups are presented as frequencies expressed in fractions of a unit, and are interpreted as estimates of the risks of the disease.

The transition to aggregated data occurs according to the following formula:

оказывается наибольшей в плотно заселенных загрязненных районах и наоборот,

- суммарная численность населения в i-х ячейках, относящихся к данной к j-й административной территории, a s - индекс, указывающий на рассматриваемый признак.where c ^(k) _s is an assessment of the degree of influence of external environmental conditions on the health of the population of a given administrative unit. Value

turns out to be the largest in densely populated contaminated areas and vice versa,

- the total population in i-cells belonging to the given j-th administrative territory, as - an index indicating the sign under consideration.

At the preliminary stage of data processing, normalization of the initial features is included. When normalizing the data of geochemical information, the ratio of the values of the concentrations of chemical elements to the average values seems to be the most correct. The incidence rate is appropriate to normalize to the average values along the edge of the corresponding values.

At the second stage, risks are modeled. The vectors of enlarged geochemical features are used as explanatory factors, the risk of a thyroid disease associated with iodine deficiency is alternately chosen as the explained variable: congenital iodine deficiency syndrome (for children and adolescents), diffuse (endemic) goiter, multinodal (endemic) goiter, subclinical hypothyroidism.

In this case, the population density of the studied administrative territory is taken into account: the higher the density, the more massive the consequences of adverse environmental conditions will have.

For subsequent clustering, the following options for linking feature vectors are possible:

1. Geochemical composition of soils: elements of the first and second hazard classes.

2. Morbidity statistics for various age groups: children's, teenage, adult.

These values of the concentration of chemical elements in the soils of PCs were used to carry out the classification of soils by chemical composition. Each sample was characterized by the coordinates and values of the concentrations of chemical elements at this point. For subsequent mathematical processing, the samples were averaged within the cells with the side Δx in longitude and Δy in latitude. The initial measurements were assigned three indices indicating the cell number, samples within the cell and the measured chemical element:

where S is the total number of chemical elements taken into account, N ^(m) is the number of samples in the m cell, M is the number of sampling cells.

Each cell with number m is associated with a vector of averaged concentrations of chemical elements in the soil:

In order to eliminate the loss of computational accuracy during computer processing of ME concentration data differing by a factor of a thousand, they were subjected to a normalization transformation, aligning orders and bringing their values to a single range

When processing the data of ME concentrations in PC soils, the following normalizing transformations were used:

1. Normalization of standard deviation (standard deviation)

Normalization on the standard deviation is convenient for identifying features associated with the absolute spread of values relative to the average. Moreover, the deviation of each component of the feature vector from the average value is normalized to the corresponding standard deviation.

2. Normalization to average

3. Normalization to the background, which is a variation of the previous

Normalization of the mean and background differ in that only large relative deviations from the mean (background) become significant.

Characteristics and cluster ranking

As signs, the concentrations of all 28 elements are considered. As the most significant 20 selected chemical elements that pose the greatest health hazard: Sn, Pb, Zn, Cu, Ag, V, Cr, Ni, Mn, Co, Mo, W, As, Bi, Li, Ba, Be, Sr , P, Sb. The elements of only the first, second and third hazard classes with known approximate permissible concentrations of MPC and maximum permissible concentrations (MPC) of chemical elements in soils taking into account hygienic standards (GN, 1995), as well as sanitary standards for permissible concentrations of chemical substances in soils ( SANNPin, 1988).

Based on the values of the concentrations of the selected chemical elements, the pollution index (SDR) for each cell is calculated:

To rank the territories according to the degree of pollution, the following SDR gradation was used:

- up to 8 - a satisfactory situation;

- 8-16 - permissible;

- 16-32 - intense;

- above 32 - critical.

To refine the standard classification of the territory, the standard SDR methodology is supplemented by the clustering procedure. The classification stage makes it possible to identify within each hierarchical category (many cells with close SDR values) the characteristic complexes of chemical elements that determine the nature and are responsible for the level of total pollution of a particular territory. This makes it possible not only to establish territories with one or another total pollution, but also to identify types of pollution by the composition of the dominant chemical elements.

According to the results of normalization of the data on the geochemical composition of soils, not average concentrations, the entire territory of the region was divided into 12 clusters, which were distributed across four levels of SDR values. The number of clusters was determined by the optimal value, which is a minimum for the Akaike criterion (table).

Table Clustering of the territory of the Primorsky Territory by the level of SDR values No. of clusters Geographical and administrative characteristics SDR values (pollution degree) I East and Central Sikhote-Alin provinces (areas: Kavalerovsky, Dalnegorsky, Terneysky, Olginsky, Chuguevsky; Vladivostok) > 32 (critical) II West- and Central-Sikhote-Alin provinces (areas: Lesozavodsky, Dalnerechensky and Chuguevsky) 16-32 (intense) III South Primorsky mountain-valley province (areas: Lazovsky and Partizansky) 16-32 (intense) IV Ussuro-Khankai, Western Sikhote-Alin provinces (areas: Khankai, Border, Khorolsky, Chernihiv, Spassky,
Yakovlevsky, Chuguevsky) > 32 (critical) v Ussuro-Khankai and Sikhote-Alin provinces (areas: Border, Khankai, Chernihiv, Kirov, Chuguevsky, Lesozavodsky, Dalnegorsky, Dalnerechensky, Terneysky) > 32 (critical) VI Central Sikhote-Alin and South Primorsky provinces (areas: Partizansky, Anuchinsky, Chuguevsky) > 32 (critical) VII South Primorsky, Ussuro-Khankaisk provinces (areas: Mikhailovsky, Anuchinsky, Spassky, Shkotovsky; Vladivostok, Partizansk) 16-32 (intense) VIII Khasan-Grodekov and East Sikhote-Alin provinces (areas: Khasansky, Olginsky, Kavalerovsky, Dalnegorsky; Vladivostok) 16-32 (intense) IX Ussuro-Khankaisk, West- and Central-Sikhote-Alin provinces (areas: Border, Khasansky, Spassky, Yakovlevsky, Dalnerechensky, Chuguevsky) <8 (satisfactory) X South Primorsky Province (areas: Shkotovsky, Partizansky, Anuchinsky; Partizansk) 16-32 (intense) Xi Khasano-Grodekovskaya, East Sikhote-Alin provinces (areas: Khasansky, Kavalerovsky, Dalnegorsky) > 32 (critical) XII Ussuro-Khan, Central and East Sikhote-Alin provinces (areas: Border, Khanka, Spassky, Chuguevsky, Dalnegorsky, Krasnoarmeysky, Terney) 16-32 (intense)

At the third stage, risk models are used to obtain assessments of the investigated risk at all points with known values of geochemical features. The result of this stage is the field of values of the mapped characteristic. Thus, data on the incidence of thyroid gland receive a coordinate reference.

The data obtained are used to build maps. On the maps there are areas characterized by increased or decreased risk of developing IDS among the population of this territory (Figs. 1-4). Increased risk assessments of all thyroid diseases in all age groups are characterized by the Spassky, Khorolsky, Khankaysky and Chernihiv regions, the soil of which contains cobalt, manganese, chromium, tungsten, nickel, arsenic and lead in high concentrations. In the South Primorsky zone, in areas directly adjacent to large settlements (Vladivostok, Artem, Nakhodka, Fokino, Bolshoi Kamen), a high risk of IDS in children and adolescents is associated with an increased content of lead, manganese, zinc in the OS, nickel, tungsten and copper.

Thus, the above information indicates that the claimed method of assessing the risk of developing iodine deficiency in the population of the administrative territory under the conditions of anthropogenic chemical environmental pollution meets the required criteria for patentability and has significant advantages compared with the known methods for diagnosing IDS. Using the proposed method allows with a high degree of probability to quantify the real and potential risks of developing IDS and the occurrence of thyroid diseases associated with iodine deficiency in conditions of anthropogenic chemical environmental pollution.

Literature

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2. Fast V.V., Boev V.M., Borschuk E.L. et al. Choice of priority indicators of population health. // Inform. Bull. “Health of the population and the environment” - 2002. - No. 8. - S. 42-45.

3. Maimulov V.G., Nagorny S.V., Shabrov A.V. The basics of system analysis in environmental hygiene research. - SPb., 2001 .-- 418 p.

4. Problems of assessing the risk to public health from environmental factors. Ed. Acad. RAMS Yu.A. Rakhmanin and G.G. Onishchenko. - Moscow, 2004 .-- 355 p.

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Claims (1)

A method for predicting the risk of iodine deficiency in the population of the administrative territory under the conditions of anthropogenic chemical environmental pollution, characterized in that determine the indicator of environmental pollution for each chemical element that is dangerous for each of the age group of health (P _x ), determine for each region of the study area the incidence of the thyroid gland (thyroid gland) associated with the iodine deficiency state (IDS), and the incidence is determined for different age groups, and on the basis of the incidence detected, the probability of the development of IDS (D _x ) is determined, on the basis of the incidence of thyroid disease associated with IDS, determine the nosological forms of diseases determine the risk of developing various nosological forms of thyroid diseases associated with IDS, according to the formula R _x = P _x D _x , where x is any chemical ecotoxicant; put the risks on a map of the area, reflecting the incidence in the area, on the basis of which a risk forecast for the development of an iodine deficiency condition is carried out.

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