Environmental health risk source identification method
By calculating pollutant emissions and carcinogenicity, and establishing a risk source strength and sensitivity matrix, the problems of high monitoring data requirements and difficulty in tracing sources in existing technologies are solved, and the rapid identification of environmental health risk sources and the clarification of enterprise management and control targets are achieved.
Patent Information
- Application Number
- CN202510966081.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-14
- Publication Date
- 2025-10-17
AI Technical Summary
Existing technologies require a lot of money and effort to obtain monitoring data, and are unable to trace the source of environmental health risks, resulting in inefficient assessments.
By calculating pollutant emissions and carcinogenicity, a health risk source strength and sensitivity matrix is established to quickly screen and classify risk sources, identify characteristic pollution factors, and clarify the environmental health risk level of the enterprise.
It has achieved rapid identification of environmental health risk sources, reduced monitoring data requirements, improved assessment efficiency and traceability capabilities, and clarified the objects of enterprise management and control.
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Figure CN120806645A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of environmental health risk source identification, and particularly relates to an environmental health risk source identification method. BACKGROUND
[0002] With the rapid development of the economic society, the substantial improvement of people's living standards and the significant improvement of the ecological environment, the public has put forward higher requirements for effectively protecting the environmental rights and interests and health rights and interests of citizens, and it is urgent to pay attention to and strengthen the management of the ecological environment and health, and effectively improve the happiness and sense of gain of the people. At present, the regional environmental health risk assessment methods in China are respectively "Technical Specification for Health Risk Assessment of Atmospheric Pollution" (WS / T 666-2019) and "Technical Guidelines for Health Risk Assessment of Regional Environmental Pollution" (TCSES 36-2021), and the two methods can calculate the human health risk through the monitored pollutant concentration. Although the above method can calculate the health risk of human exposure to pollutants, it has the following technical defects: First, because the toxicity of each pollutant is different, especially hundreds of volatile organic pollutants such as hydrocarbons, halogenated hydrocarbons, oxygen hydrocarbons and nitrogen hydrocarbons, a large amount of effort and funds are needed to obtain monitoring data to realize the calculation in the early stage.
[0003] Second, after calculating the regional environmental health risk, if it is judged to be at risk, it is necessary to trace back to find the polluting enterprises, so it has certain limitations. SUMMARY
[0004] In order to solve the above problems existing in the prior art, the purpose of the present application is to provide an environmental health risk source identification method, which overcomes the technical defects of the prior art that a large amount of monitoring data needs to be obtained with funds and effort, and the source cannot be traced.
[0005] The technical scheme adopted by the present application is: An environmental health risk source identification method, comprising the following steps: S1: Health risk source intensity calculation and grading: the health risk source intensity is calculated according to the pollutant emission amount of the risk source and the carcinogenic intensity / reference dose of the pollutant, and the grading is determined according to the source intensity quantile table of the same industry; S2: Sensitivity calculation and grading: the hazard area of the risk source is determined through the geographical characteristics of the risk source, the sum of the number of people in the hazard area is calculated, and the grade is calculated according to the different sum of the number of people; S3: Risk grading: the risk grading matrix is determined according to the risk level of the risk source and the sensitivity of the receptors in the hazard area.
[0006] The rapid screening and grading of the method risk source of the application is based on the carcinogenic / non-carcinogenic risk of the characteristic pollutants of the semi-quantitative risk source emission to the surrounding population receptor, and the evaluation work content includes health risk source intensity calculation and grading, sensitivity calculation and grading and risk grading.
[0007] The application firstly considers the source problem by establishing the environmental health risk source identification method, determines the enterprise environmental health risk grading through establishing the environmental health risk source intensity and sensitivity matrix, thereby clearly defines the enterprise control object with environmental health risk, and identifies the characteristic pollution factor, thereby providing a basic basis for preventing the regional environmental health risk. The application can overcome the technical defects in the prior art that a large amount of monitoring data needs to be obtained by spending funds and energy, and the source cannot be traced.
[0008] As a preferred scheme of the application, in step S3, after the risk grading matrix is determined, the health risk level of the risk source is divided into: no risk source, low risk source, medium risk source, high risk source and extremely high risk source.
[0009] As a preferred scheme of the application, in step S1, the environmental health risk source intensity calculation specifically includes the following steps: S11: waste gas pollutant health risk source intensity calculation: The health risk source intensity of a single atmospheric pollutant can be calculated according to the following formula: ; Wherein: is the health risk source intensity of the atmospheric pollutant x; is the emission amount of the atmospheric pollutant x; is the industry emission coefficient of the atmospheric pollutant x; is the respiratory inhalation carcinogenic slope factor of the atmospheric pollutant x; 61.8 is the average adult weight; The health risk source intensity of multiple atmospheric pollutants can be calculated according to the following formula: ; Wherein, is the health risk source intensity of multiple atmospheric pollutants; S12: waste water pollutant health risk source intensity grading: The waste water pollution source hazard intensity is quantitatively calculated according to the industrial enterprise waste water emission amount.
[0010] As a preferred scheme of the application, in step S1, the health risk source intensity grading is specifically: On the basis of the pollution source hazard intensity calculation, according to the pollution source hazard intensity of different enterprises, the industrial enterprises of the same industry category in the evaluation area are sorted from small to large; according to the relative position of the sorting, the hazard intensity is graded, and the hazard intensity value of 0 is not involved in the sorting.
[0011] As a preferred scheme of the present application, when the health risk source intensity is graded, the enterprises with the hazard intensity ranking position in the first 1 / 3 are classified as P1 level, the enterprises with the hazard intensity ranking position in the middle 1 / 3 are classified as P2 level, and the enterprises with the hazard intensity ranking position in the last 1 / 3 are classified as P3 level.
[0012] As a preferred scheme of the present application, the step S2 specifically comprises the following steps: S21: waste gas pollutant sensitivity grading: the waste gas sensitivity refers to the degree of harm to the population in the surrounding area of the enterprise caused by the toxic atmospheric pollutants emitted by the enterprise; S22: waste water pollutant sensitivity grading: the water source sensitivity refers to the degree of harm to the population in the surrounding water area of the enterprise caused by the different directions of the toxic waste water emitted by the enterprise.
[0013] As a preferred scheme of the present application, the step S21 specifically comprises: The sensitivity of the population in the influence range of the risk source is graded according to the population number in the harm area to the sensitivity of the receptors around the risk source; wherein, the population number within 5km is greater than 50,000, which is classified as E3 level, the population number within 5km is 1-50,000, which is classified as E2 level, and the population number within 5km is less than 10,000, which is classified as E1 level.
[0014] As a preferred scheme of the present application, the step S22 specifically comprises: According to the total discharge type and direction of the waste water of the enterprise, it is divided into 10 categories; according to whether the waste water of the enterprise is directly discharged into rivers, lakes, seas or discharged into sewage treatment plants and the risk impact on health, the sensitivity of the water source receptors is graded into three levels; wherein, the waste water entering the urban sewage treatment plant and the industrial waste water centralized treatment plant is classified as E1 level; the waste water entering the urban sewer and then entering the rivers, lakes, reservoirs / entering the urban sewer and then entering the coastal watershed / entering the ground seepage or evaporation area / entering other units is classified as E2 level; the waste water directly entering the sea / directly entering the rivers, lakes, reservoirs / directly entering the sewage irrigation farmland is classified as E3 level.
[0015] As a preferred scheme of the present application, the step S3 specifically comprises: The enterprise with the highest level of sensitivity and hazard intensity is classified as an extremely high risk source, and the level is I; the enterprise with one of the highest level of hazard intensity or sensitivity and the other of the second highest level is classified as a high risk source, and the level is II; the enterprise with one of the highest level of hazard intensity or sensitivity and the other of the lowest level, or both of the second highest level is classified as a medium risk source, and the level is III; the enterprise with one of the second highest level of hazard intensity or sensitivity and the other of the lowest level, or both of the lowest level is classified as a low risk source, and the level is IV.
[0016] The present application has the following beneficial effects: The present application firstly considers the source problem by establishing an environmental health risk source identification method, determines enterprise environmental health risk classification through establishing an environmental health risk source intensity and sensitivity matrix, thereby clearly defining the enterprise environmental health risk control object, and identifying the characteristic pollution factor, and providing a basis for preventing the environmental health risk in the region. The present application can overcome the technical defects in the prior art that a large amount of monitoring data needs to be obtained by spending funds and energy, and the source cannot be traced. BRIEF DESCRIPTION OF DRAWINGS
[0017] Figure 1 is a method flowchart of the present application; Figure 2 is an environmental health risk industry screening principle and basis schematic diagram. DETAILED DESCRIPTION
[0018] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.
[0019] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.
[0020] The rapid screening and grading of the method risk source of the present application is based on the carcinogenic / non-carcinogenic risk of the characteristic pollutants emitted by the semi-quantitative risk source to the surrounding population receptors, and the evaluation work content includes health risk source intensity calculation and grading, sensitivity calculation and grading, and risk grading.
[0021] As shown in Figure 1 the environmental health risk source identification method of the present embodiment includes the following steps: S1: health risk source intensity calculation and grading (P): the health risk source intensity is calculated according to the pollutant emission amount of the risk source and the carcinogenic intensity / reference dose of the pollutant, and the grading is determined according to the source intensity quantile table of the same industry; S2: sensitivity calculation and grading (E): the harm area of the risk source is determined through the geographical characteristics of the risk source, the sum of the number of people in the harm area is calculated, and the grade is calculated according to the different sum of the number of people; S3: risk classification (R): according to the risk level (P) of the risk source and the sensitivity (E) of the receptors in the hazard area, a risk classification matrix is determined; the health risk level of the risk source is divided into: no risk source, low risk source, medium risk source, high risk source and extremely high risk source.
[0022] The present application firstly considers the source problem by establishing an environmental health risk source identification method, determines the environmental health risk classification of enterprises by establishing the environmental health risk source intensity and sensitivity matrix, thereby clearly determines the environmental health risk enterprise control object, and identifies the characteristic pollution factor, and provides a basis for preventing the environmental health risk in the region. The present application can overcome the technical defects that a large amount of monitoring data needs to be obtained by spending funds and energy and cannot be traced in the prior art.
[0023] Specifically, in step S1, the environmental health risk source intensity calculation specifically includes the following steps: S11: waste gas pollutant health risk source intensity calculation: The health risk source intensity of a single atmospheric pollutant can be calculated according to the following formula: .
[0024] Wherein: is the health risk source intensity of atmospheric pollutant x, dimensionless; is the emission amount of atmospheric pollutant x, kg; is the industry emission coefficient of atmospheric pollutant x (specifically VOC); is the respiratory inhalation carcinogenic slope factor of atmospheric pollutant x, (mg pollutant•kg -1 body weight•d -1 ) -1 ; 61.8 is the average weight of an adult, kg.
[0025] The health risk source intensity of multiple atmospheric pollutants can be calculated according to the following formula: ; Wherein, is the health risk source intensity of multiple atmospheric pollutants, dimensionless.
[0026] S12: waste water pollutant health risk source intensity classification: Due to the difficulty in accounting for the emission of single pollutant in waste water of enterprises, considering that the types of waste water emission pollutants in the same industry have convergence, the waste water pollution source hazard intensity is quantitatively calculated according to the waste water emission amount of industrial enterprises.
[0027] In step S1, the health risk source intensity classification is specifically: On the basis of pollution source hazard intensity calculation, according to the hazard intensity of different enterprises, the industrial enterprises of the same industry in the evaluation area are sorted from small to large. According to the relative position of the sorting, the hazard intensity is divided into three grades, P1-P3. Among them, the hazard intensity value of 0 (no waste gas / wastewater discharge) does not participate in sorting, the enterprises whose hazard intensity sorting position is located in the front 1 / 3 are P1 grade, the enterprises whose hazard intensity sorting position is located in the middle 1 / 3 are P2 grade, and the enterprises whose hazard intensity is the largest 1 / 3 are P3 grade. According to the health risk source intensity P, the sorting position of the same industry in the country is divided, as shown in Table 1.
[0028] Table 1: Health risk source intensity grade division:
[0029] Specifically, step S2 specifically includes the following steps: S21: Sensitivity refers to the degree of harm to the population around the enterprise that emits toxic air pollutants. The sensitivity of the population in the risk source influence area is graded according to the population number in the hazard area in the “Enterprise Environmental Emergency Risk Wind Level Method” (HJ 941-2018). Among them, the population within 5km is more than 50,000, which is divided into E3 grade, 1-50,000 people is E2 grade, and less than 10,000 is E1 grade, as shown in Table 2.
[0030] Table 2: Sensitivity type division of receptors in risk source influence area:
[0031] S22: Water source sensitivity refers to the harm to the water area and population around the enterprise that emits toxic wastewater. According to the “Wastewater Discharge Destination Code” (HJ 523-2009), the total discharge type and destination of enterprise wastewater are divided into 10 categories (A, B, C, D, E, F, G, H, K, L). According to whether the enterprise wastewater is directly discharged into rivers, lakes, seas or discharged into sewage treatment plants and other ways and the impact on health, the sensitivity of the water receptor is divided into three grades. Among them, into the city sewage treatment plant and industrial wastewater centralized treatment plant is divided into E1 grade; into city sewer (re-enter rivers, lakes, reservoirs) / into city sewer (re-enter coastal waters) / into evaporation or into other units / other is divided into E2 grade; directly into the sea / directly into rivers, lakes, reservoirs, etc. / directly into sewage irrigation farmland is divided into E3 grade.
[0032] Table 3: Sensitivity type division of receptors in risk source influence area:
[0033] In particular, step S3 is specifically: The enterprise environmental health risk classification is determined by the possibility of health hazards and the sensitivity of population exposure. According to the health risk source intensity level (P) and the sensitivity of the receptor in the danger area (E), the classification matrix is shown in the following table. The enterprises with the highest level of sensitivity and hazard intensity are classified as extremely high risk sources, level I; one of the hazard intensity or sensitivity is the highest level, and the other is the next highest level, classified as high risk sources, level II; one of the hazard intensity or sensitivity is the highest level, and the other is the lowest level, or both are the next highest level, classified as medium risk sources, level III; one of the hazard intensity and sensitivity is the next highest level, and the other is the lowest level, or both are the lowest level, classified as low risk sources, level IV.
[0034] Among them, the risk of waste gas and waste water pollutants, carcinogenic / non-carcinogenic risk classification is carried out separately, and the highest level is the risk classification level.
[0035] Table 4 Risk source health risk classification matrix:
[0036] Example: Step 1: Screening of environmental health risk key industries in Chengdu: As shown in Figure 2 , the environmental health risk industry should meet the following conditions in principle. One is that the health hazards are clear, and toxic and harmful pollutants are discharged or have caused group health damage events; two is that it belongs to the key supervision industry involved in national or local management specifications and policy documents; three is that it belongs to the industry involved in national or local industry emission standards, and the supervision efficiency is guaranteed, avoiding unreasonable use of resources. 14 key industries in a certain place are screened out.
[0037] Step 2: Data preparation: 1. Industrial enterprise basic information: Based on the data sources of pollution source survey, pollution discharge permit, environmental statistics, etc., the enterprise name, geographic location (central longitude and latitude), industry category, running status, pollution generating process and facility situation, etc. of the above-mentioned 14 industries are obtained.
[0038] 2. Industrial enterprise pollution emission data: 2.1 Waste gas pollutant emission data: Based on the information sources such as pollution source census, pollution discharge permit, and ecological environment monitoring, the industrial enterprise waste gas pollutant emission data are directly obtained, including waste gas emission port information, waste gas emission amount, and emission amount of sulfur dioxide, nitrogen oxides, particulate matter, volatile organic compounds, ammonia, arsenic, lead, cadmium, chromium, mercury, etc. Among them, the emission data of toxic heavy metals such as arsenic, lead, cadmium, chromium, mercury, volatile organic pollutants, and industrial wastewater are focused on in the risk source identification process.
[0039] The pollutant emission amount of heavy metals directly quotes the pollution emission statistical data. The pollutant emission amount of organic matter is calculated according to the pollution factor emission amount by means of the emission coefficient method. The calculation formula based on the emission quality is as follows.
[0040] ; Among them: e i，j，k is the emission amount of pollution factor k of enterprise j of industry i, g; k i，k is the mass proportion of pollution factor k emitted by industry i, wt%; m i，j，k is the VOCs waste gas emission quality of enterprise j of industry i, kg.
[0041] The calculation formula based on the industrial waste gas emission amount is as follows.
[0042] ; Among them: e i，j，k is the emission amount of pollution factor k of enterprise j of industry i, g; c i，k is the concentration coefficient of pollution factor k emitted by industry i, mg / m 3 ; V i，j，k is the VOCs waste gas emission volume of enterprise j of industry i, m 3 .
[0043] 2.2 Waste water pollutant emission data: Based on the information sources such as pollution source census, pollution discharge permit, and ecological environment monitoring, the industrial enterprise waste water pollutant emission data are directly obtained, including industrial enterprise waste water emission amount (kg) and waste water emission destination.
[0044] 2.3 Pollutant parameters: 2.3.1 Physical and chemical property parameters of pollutants: The pollution physical and chemical property parameters required for risk assessment include dimensionless Henry constant (H'), air diffusion coefficient (Da), water diffusion coefficient (Dw), soil-organic carbon distribution coefficient (Koc), and water solubility (S).
[0045] 2.3.3 Non-carcinogenic effect toxicity parameters: Non-carcinogenic effect toxicity parameters include respiratory inhalation reference concentration (RfC), respiratory inhalation reference dose (RfDi).
[0046] Respiratory inhalation reference dose (RfDi) is extrapolated from respiratory inhalation reference concentration (RfC).
[0047] 2.3.4 Other related parameters of pollutants: Other related parameters include oral intake absorption factor (ABS).
[0048] 2.4 Regional population data: Through the "China population spatial distribution kilometer grid data set", the population data of the evaluation area is obtained. The base map containing population data information and the risk source point map of toxic pollutant emission are imported into ArcGIS, and a buffer zone (radius 5 km range) is established with the risk source point as the center, and the total population number in the buffer zone range is extracted.
[0049] Step three: environmental health risk source intensity calculation and classification: The health risk source intensity of waste gas pollutants is calculated by the formula mentioned above, and the harm intensity of waste water pollution sources is quantitatively calculated according to the waste water discharge of industrial enterprises. According to the relative position of the sorting result, the harm intensity is classified into three grades of P1-P3, among which the harm intensity value of 0 (no waste gas emission) does not participate in sorting, the enterprises with harm intensity sorting position in the first 1 / 3 are P1 grade, the enterprises with harm intensity sorting position in the middle 1 / 3 are P2 grade, and the enterprises with harm intensity of 1 / 3 are P3 grade.
[0050] Step four: Sensitivity classification: Waste gas pollutants are classified according to the harm to the population around the risk source, among which the population within 5km is more than 50,000, classified as E3 grade, 1-50,000 people as E2 grade, and less than 10,000 as E1 grade. Waste water pollutants are classified according to the discharge destination, into city sewage treatment plant and industrial waste water centralized treatment plant, classified as E1 grade; into city sewer (re-enter rivers, lakes, reservoirs) / into city sewer (re-enter coastal watershed) / into seepage or evaporation land / into other units / other, classified as E2 grade; directly into sea / directly into rivers, lakes, reservoirs and other water environments / directly into pollution irrigation farmland, classified as E3 grade.
[0051] Step five: Environmental health risk source classification: Considering the harm intensity of pollution sources (P) and the sensitivity of waste gas / waste water pollutants (E), a risk source classification matrix model is established to classify the risk sources.
[0052] The present application is not limited to the above-mentioned optional embodiments, and anyone can derive other various forms of products under the inspiration of the present application, but regardless of any changes in shape or structure, any technical solutions falling within the scope defined by the claims of the present application fall within the protection scope of the present application.
Claims
1. A method for identifying environmental health risk sources, characterized by: The following steps are involved: S1: Calculation and classification of health risk source strength: The health risk source strength is calculated based on the pollutant emissions and the carcinogenicity / reference dose of the pollutants, and the classification is determined based on the source strength quantile table of the same industry; S2: Sensitivity calculation and classification: Determine the hazard area of the risk source based on its geographical characteristics, calculate the sum of the number of people in the hazard area, and calculate the level based on the sum of different numbers of people; S3: Risk classification: A risk classification matrix determined based on the risk level at the risk source and the sensitivity of the receptors in the hazard area.
2. The method for identifying environmental health risk sources according to claim 1, characterized in that: In step S3, after the risk grading matrix is determined, the health risk levels of risk sources are divided into: no risk source, low risk source, medium risk source, high risk source and extremely high risk source.
3. The method for identifying environmental health risk sources according to claim 1, characterized in that: In step S1, the calculation of environmental health risk source strength specifically includes the following steps: S11: Calculation of health risk source strength of exhaust gas pollutants: The health risk source intensity of a single air pollutant can be calculated according to the following formula: ； in: is the health risk source intensity of air pollutant x; is the emission of air pollutant x; is the industry emission coefficient of atmospheric pollutant x; is the carcinogenic slope factor of inhalation of air pollutant x; 61.8 is the average weight of adults; The health risk source strength of various air pollutants can be calculated according to the following formula: ； in, It is a strong source of health risks for a variety of air pollutants; S12: Classification of health risk sources of wastewater pollutants: The hazard intensity of wastewater pollution sources is quantitatively calculated based on the wastewater discharge volume of industrial enterprises.
4. The method for identifying environmental health risk sources according to claim 1, characterized in that: In step S1, the health risk source intensity classification is specifically as follows: Based on the calculation of pollution source hazard intensity, industrial enterprises in the same industry category within the evaluation area are ranked from small to large according to the pollution source hazard intensity of different enterprises; the hazard intensity is divided into levels according to the relative position of the ranking, and those with a hazard intensity value of 0 are not included in the ranking.
5. The method for identifying environmental health risk sources according to claim 4, characterized in that: When grading health risk source strength, enterprises in the top 1 / 3 of the hazard intensity ranking are rated P1, enterprises in the middle 1 / 3 are rated P2, and the 1 / 3 of enterprises with the greatest hazard intensity are rated P3.
6. The method for identifying environmental health risk sources according to claim 1, characterized in that: Step S2 specifically includes the following steps: S21: Exhaust gas pollutant sensitivity classification: Exhaust gas sensitivity refers to the extent to which the size of the population in the area surrounding the enterprise may be harmed by the emission of toxic air pollutants by the enterprise; S22: Sensitivity classification of wastewater pollutants: Water source sensitivity refers to the degree of harm to the surrounding waters and people caused by the different destinations of toxic wastewater discharged by enterprises.
7. The method for identifying environmental health risk sources according to claim 6, characterized in that: Step S21 is specifically as follows: The sensitivity of the population within the impact range of the risk source is graded according to the population size of the hazard area. Among them, the population within 5km is greater than 50,000 and is classified as E3 level, the population within 5km is 10,000 to 50,000 and is E2 level, and the population within 5km is less than 10,000 and is E1 level.
8. The method for identifying environmental health risk sources according to claim 6, characterized in that: Step S22 is specifically as follows: According to the total discharge type and destination of enterprise wastewater, it is divided into 10 categories; according to whether the enterprise wastewater is discharged directly into rivers, lakes, seas or into sewage treatment plants, as well as the risk impact on health, the water source receptor sensitivity classification is divided into three levels; among them, those entering urban sewage treatment plants and centralized industrial wastewater treatment plants are classified as E1 level; those entering urban sewers and then entering rivers, lakes, reservoirs / entering urban sewers and then entering coastal waters / entering ground infiltration or evaporation areas / entering other units are classified as E2 level; those directly entering the sea / directly entering rivers, lakes, reservoirs and other water environments / directly entering sewage-irrigated farmland are classified as E3 level.
9. The method for identifying environmental health risk sources according to claim 1, characterized in that: Step S3 is specifically as follows: Enterprises with the highest sensitivity and hazard intensity are classified as extremely high risk sources, level I; enterprises with either hazard intensity or sensitivity at the highest level and the other at the second highest level are classified as high risk sources, level II; enterprises with either hazard intensity or sensitivity at the highest level and the other at the lowest level, or both at the second highest level, are classified as medium risk sources, level III; enterprises with either hazard intensity or sensitivity at the second highest level and the other at the lowest level, or both at the lowest level, are classified as low risk sources, level IV.