Notice on Issuing the Framework Guide on Technical Methods for Environmental Risk Assessment of Chemical Substances (for Trial Implementation)

In order to strengthen the environmental management of chemical substances, establish and improve the technical method system for environmental risk assessment of chemical substances, and standardize and guide the environmental risk assessment of chemical substances, the Ministry of Ecology and Environment and the Health Commission have organized and compiled the "Framework Guide for Technical Methods for Environmental Risk Assessment of Chemical substances (for trial implementation)", which is hereby issued.

General Office of the Ministry of Ecology and Environment

General Office of the Health Commission

26 August 2019

(This social public)

Copy to: Ecological Environment Departments (Bureaus), Health and Health Committees of all provinces, autonomous regions, and municipalities directly under the Central Government, Ecological Environment Bureau and Health Committee of Xinjiang Production and Construction Corps.

Issued by the General Office of the Ministry of Ecology and Environment on September 3, 2019

Framework Guide for Technical Methods for Environmental Risk Assessment of Chemical Substances

(Trial)

Assessing the environmental risks of chemical substances is a prerequisite for the safe use of chemical substances. Environmental risk assessment of chemical substances is to scientifically determine the risk degree of chemical substances to the ecological environment and human health by analyzing the inherent hazard attributes of chemical substances and their information about entering the ecological environment and exposure to human body in the whole life cycle of production, processing, use and disposal, so as to provide decision-making basis for the targeted formulation and implementation of risk control measures.

1. scope of application

This guideline specifies the basic framework for environmental risk assessment of chemical substances, and clarifies the basic points, technical requirements and reporting requirements for environmental risk assessment of chemical substances.

This guideline applies to the environmental risk assessment of different exposure routes during the normal production and use of a single chemical substance, and does not apply to the risk assessment under the condition of accidental leakage.

2. basic points

(I) Assessment Steps

Environmental risk assessment of chemical substances usually includes four steps: hazard identification, dose (concentration)-response (effect) assessment, exposure assessment and risk characterization (hereinafter referred to as "four-step method").

1. Hazard identification

Hazard identification is to determine the inherent hazard attributes of chemical substances, including ecotoxicology and health toxicology attributes.

2. Dose (concentration)-response (effect) assessment

Dose (concentration)-response (effect) evaluation is to determine the relationship between chemical exposure concentration/dose and toxic effects.

3. Exposure assessment

Exposure assessment is to estimate the degree of exposure of a chemical substance to the ecological environment or human body.

In environmental risk assessment, it is usually expressed as the concentration of chemical substances in the environment; in health risk assessment, it is usually expressed as the total exposure of chemical substances in the human body.

4. Risk characterization

Risk characterization is based on chemical hazard identification, dose (concentration)-response (effect) assessment and exposure assessment, qualitative or quantitative analysis of the probability and degree of risk caused by chemical substances to the ecological environment and human health.

Not all risk assessments need to go through the full four steps described above. If the hazard identification and dose (concentration)-response (effect) assessment indicate that the hazard to the ecological environment and human health is extremely low, no subsequent risk assessment is required; if the exposure assessment indicates that an exposure pathway does not exist, the subsequent risk assessment under that exposure pathway may be terminated. In addition, in order to improve the efficiency of risk assessment and reduce the cost of risk assessment, risk assessment is usually based on existing data, and the risk under reasonable worst-case scenarios is assessed in a relatively conservative manner. If no unreasonable risks are found in chemical substances, the assessment process is terminated. If the risk is worthy of attention, more detailed data information is collected and further detailed risk assessment is carried out.

(II) assessment conclusion

Environmental risk assessment of chemical substances usually has the following three conclusions:

1. No unreasonable risks have been found, and the assessment conclusion is based on the existing data. Before new information is obtained, no new risk prevention and control measures need to be taken for the time being.

2. There are unreasonable risks and further risk prevention and control measures are needed to reduce the risks.

3. The risk cannot be determined and information on the chemical substance needs to be supplemented (including further toxicity testing) and the risk assessment needs to be repeated.

(III) uncertainty analysis

Risk assessment is based on current scientific understanding and limited data. It is difficult to obtain extremely accurate data on chemical hazards and exposures, so there is uncertainty in risk assessment. An uncertainty analysis should be carried out to identify all sources of uncertainty in the risk assessment process that affect the assessment conclusions, and sensitivity analysis should be carried out if necessary.

Combined with risk management objectives, in order to reduce the uncertainty of risk assessment, further research and collection of toxicity and exposure data related to chemical substances can be carried out continuously and repeatedly, I .e. risk assessment can be an iterative process.

(IV) data quality assessment

In the risk assessment, the quality of toxicity data and exposure data of the chemical substances used needs to be evaluated.

In general, toxicity data focus on assessing relevance, reliability, and adequacy. Relevance refers to the degree to which data and test methods are applicable to hazard identification or risk characterization. Reliability refers to the inherent quality of the toxicity test data, related to the test method and the clarity and logic of the test process and results. Adequacy means that toxicity data are sufficient to support a judgment about certain hazards or risks.

For exposure data, if measured exposure data is used, the focus is usually on assessing reliability and representativeness, with a comprehensive assessment of measured sampling and analysis methods, number of samples, sampling points, measured geospatial and temporal scales. If the model is used to calculate the data, the applicability of the model, the accuracy of the model input parameters, etc. should be fully evaluated.

Spatial scale of (V) exposure assessment

Exposure assessment can usually be carried out on two spatial scales, one is the point source scale, which refers to the spatial area near the point source of the chemical substance, which usually represents the most unfavorable exposure situation, and the other is the regional scale, which refers to the larger spatial area relative to the point source scale, which usually represents the average exposure situation.

The two spatial scale exposure scenarios are generally the simulation and standardization of the actual place.

(VI) Risk Assessment for PBT and vPvB Chemicals

PBT chemicals are chemicals that are persistent, bioaccumulative and toxic, and vPvB chemicals are chemicals that are highly persistent and bioaccumulative. PBT and vPvB chemicals can accumulate in the environment for a long time and accumulate in organisms, and their long-term effects are difficult to predict; moreover, this environmental accumulation is irreversible to some extent, and even if emissions are stopped, the environmental concentration of chemicals does not necessarily decrease.

For chemicals belonging to the PBT and vPvB classes, the application of the above-mentioned "four-step method" to carry out quantitative risk assessment has great uncertainty, and it is not possible to derive safe concentrations with sufficient reliability. The focus is usually on the identification of emission and exposure characteristics, that is, the identification of the release of PBT and vPvB chemicals to the environment throughout the life cycle, as well as all possible exposure routes of the chemical to humans and the environment. On the basis of the above, measures to reduce emissions and exposure to humans and the environment are proposed.

Factors to be considered in risk assessment of (VII) metals and their compounds

Compared with organic chemicals, metals and their compounds should be considered in risk assessment due to their own characteristics. Highlights include:

1. Natural background properties. Metals and their compounds are usually naturally occurring components of the environment, with background concentrations in nature, and background concentrations vary greatly from geographic region to geographic region. Humans and animals and plants may have some adaptability to different levels of metals over the long term.

2. Nutritional attributes. Some metals are essential nutrients for the health of humans, animals, plants and microorganisms, but too little or too much can have negative effects.

3. Metal form. Different valence metals and different metal compounds have different biological effectiveness and toxic effects.

3. Technical Requirements

Environmental risk assessments should assess the potential risks of chemicals to inland and marine environments, as well as the human health risks of indirect exposure of chemicals through the environment.

The risk assessment of the inland environment generally includes the inland aquatic environment (including sediments), the terrestrial environment, the atmospheric environment, the top predator and the microbial environment of the sewage treatment system. Risk assessments for the marine environment generally include marine water environments (including sediments) and top predators.

Human health risk assessment through indirect exposure to the environment generally assesses human health risks through inhalation, ingestion, and skin contact. When conducting assessments, attention should be paid to the impact of chemicals on sensitive populations (e. g. pregnant women, children, the elderly, etc.).

(I) Hazard Identification

1. Environmental hazard identification

Environmental hazard identification is the determination of the ecotoxicological properties of a chemical substance, which generally include acute and chronic toxicity.

The toxicity of chemical substances to algae, daphnia and fish (representing three different trophic levels) is usually used to represent the harm to inland water environment and marine water environment, the toxicity to chironomids, silkworms, foxtail algae and other organisms is used to represent the harm to sediment, and the toxicity to plants, earthworms and soil microorganisms is used to represent the harm to terrestrial biological environment, adopting toxicity to activated sludge represents a hazard to the microbial environment of the wastewater treatment system. The hazards to the atmospheric environment usually include global warming, ozone layer depletion, acid rain and other non-biological effects, as well as specific environmental biological effects. The biological effects of chemical substances on the atmospheric environment are mainly considered in the assessment. For the assessment of top predators, emphasis is placed on the accumulation of lipophilic chemicals through the food chain.

2. Health hazard identification

Health hazard identification focuses on the carcinogenicity, mutagenicity, reproductive and developmental toxicity, repeated dose toxicity and other chronic toxicity of chemical substances, as well as sensitization. A chemical can have multiple toxicities.

Generally speaking, there are four types of data that can be used to characterize the hazards of chemical substances: epidemiological investigation data, animal in vivo experimental data, in vitro experimental data, and other data (such as computational toxicology data). Epidemiological survey data is the most reliable information to determine the harm of chemical substances to human health, but it is generally difficult to obtain; and due to the influence of many confounding factors (such as co-exposure to pollutants), target population differences, sample size, health impact lag, etc., it is difficult to determine the causal relationship between chemical substances and health hazards. At present, animal experimental data is still the main source of data for hazard identification.

(II) dose (concentration)-response (effect) assessment

1. Dose (concentration)-response (effect) assessment of environmental hazards

Using ecotoxicological data, the predicted no effect concentration (PNEC) was derived for different evaluation objects, such as PNEC water, PNEC sediment, PNEC soil, PNEC microorganism, etc. PNEC is the concentration that does not normally produce adverse effects.

PNEC values are usually derived from the lowest lethal concentration half (LC50), half effective concentration (EC50), or no observed effect concentration (NOEC) divided by the appropriate evaluation factor (AF). When the ecotoxicity data are sufficient, other methods can be used to derive PNEC, such as species sensitivity distribution.

Under normal circumstances, the water environment ecological toxicity data is relatively rich, other assessment objects such as soil, sediment and other ecological toxicological data is relatively lacking, at this time can take other methods to derive PNEC. If the soil-related data is missing, the phase equilibrium distribution method can be used to derive the PNEC of the soil environment, I .e., the PNEC soil is derived from the PNEC water and soil-water distribution coefficient (K soil-water), but the PNEC soil derived by this method is generally used to screen whether subsequent toxicity tests are needed and cannot replace the PNEC derived from soil ecotoxicological data.

2. Dose (concentration)-response (effect) assessment of health hazards

Depending on the mechanism of toxicity, the dose (concentration)-response (effect) assessment of health hazards is divided into the following two categories:

The first case is a threshold dose (concentration)-response (effect) assessment. That is, a chemical can cause a toxic effect only if it exceeds a certain dose (threshold), which is called the "no observed adverse effect dose level" (NOAEL). When NOAEL values are not available, the "Lowest Observed Adverse Effect Dose Level" (LOAEL) can be used as the toxicity threshold.

After determining the NOAEL or LOAEL value, further calculate the safety threshold for the chemical to have no harmful effects on the human body, such as the Tolerable Daily Intake (TDI), that is, the human body ingests the chemical substance below this dose every day for life, and it will not cause health hazard effects. It should be emphasized that the assumption of estimating the safety threshold is that the person is exposed throughout his or her life.

The safety threshold is generally obtained by dividing the NOAEL by the uncertainty factor (UF). Uncertainty coefficients generally take into account interspecies differences, individual differences, and other uncertainty factors (e. g., data reliability, exposure time, etc.). Due to the different metabolic effects of chemical substances in different species, individuals have different sensitivity to chemical substances. Generally, the uncertainty coefficient does not exceed 10000.

The second case is a threshold-free dose (concentration)-response (effect) assessment. That is, there is no lower limit, and the intake of any dose of chemical substances has a certain probability of causing health hazards, such as carcinogenicity related to genotoxicity. For threshold-free dose (concentration)-response (effect) assessment, the safe dose (VSD) is usually calculated by a mathematical model at a given acceptable risk probability.

In addition to the above methods, the safety threshold or safe dose of chemical substances can also be calculated by the benchmark dose method (BMD) according to the specific situation.

(III) Exposure Assessment

1. Environmental Exposure Assessment

In general, the predicted environmental concentration (PEC) of chemical substances should be derived for different evaluation objects, such as PEC water, PEC sediment, PEC soil, PECstp, etc.

The PEC can be derived based on measured data in the environment and model calculations. Considering the uncertainty of environmental exposure assessment, when PEC is obtained by environmental measured data and model calculation at the same time, the following situations should be analyzed in detail:

(1) The model calculates PEC ≈ based on the monitored PEC, indicating that the most important sources of exposure are taken into account. More credible results should be used based on professional judgment.

(2) When the model calculates PEC> PEC based on monitoring, on the one hand, the model may not simulate the actual conditions of the environment well, or the degradation process of the chemical substances is not fully considered; on the other hand, the monitoring data may not be reliable, or only represent the environmental background concentration. If the monitoring-based PEC is derived from a large number of representative samples, it should be preferred. However, if the worst-case scenario assumed by the model is reasonable, the PEC calculated by the model may be used.

(3) When the model calculates PEC

Environmental exposure assessment should consider the different situations of chemical production, use and emission, and the differences of terrain and meteorological conditions should be considered when establishing exposure scenarios. If an exposure model is used, a common standard environment is generally used, I .e., relevant default environmental parameters are pre-established. The environmental parameter may be an average value of an actual environmental parameter, or a value of an environmental parameter under a reasonable worst exposure scenario, such as temperature, density of atmosphere, water, and soil, concentration of suspended matter in the water environment, volume ratio of solid phase in suspended matter, volume ratio of water phase, weight ratio of organic carbon, and the like.

2. Health Exposure Assessment

Human health exposure assessment through environmental indirect exposure is mainly based on the predicted environmental concentration of chemical substances in surface water, groundwater, atmosphere and soil, and estimates the total daily exposure of human body to chemical substances. It is usually expressed as the external exposure dose of the chemical substance to the human body.

Three routes of exposure are generally considered: inhalation, ingestion, and skin contact.

Usually do as follows:

(1) Assess the concentration of chemical substances in the relevant media of different exposure routes in the human body.

(2) Assess the body's intake rate of each type of medium.

(3) Calculate the total intake by integrating the human body's intake rate of each medium and the concentration of chemical substances in the medium (if necessary, consider the bioavailability under each intake route).

Due to the difference of crowd behavior, the exposure of different groups is different. The choice of exposure scenario has a significant impact on the conclusion of the risk assessment. It is extremely difficult to choose an exposure scenario completely scientifically and reasonably, and it is necessary to consider all factors and make a compromise, usually choosing the "reasonable worst scenario" and the typical scenario. Exposure due to accidents and abuse is generally not considered, but risk control measures taken should be taken into account.

(IV) risk characterization

1. Environmental risk characterization

Environmental risk characterization is a qualitative or quantitative representation of the relationship between the level of exposure to a chemical substance and the predicted no-effect concentration in different assessment subjects. For the same chemical substance, the risk characterization results are different for different assessment objects of exposure.

(1) Quantitative risk characterization

For the chemical substances for which the predicted environmental concentration (PEC) and the predicted no effect concentration (PNEC) can be obtained, the PEC of the chemical substances in the evaluation object is compared with the PNEC, and the environmental risk of the chemical substances to different evaluation objects is characterized respectively.

If PEC/PNEC ≤ 1, no unreasonable environmental risk of the chemical has been found.

If PEC/PNEC>1, the chemical presents an unreasonable environmental risk.

In view of the uncertainty of risk assessment, for the above two situations, according to the specific circumstances, the weight of evidence, expert judgment and other methods can be used to determine whether further exposure and toxicity data need to be collected, and further risk assessment can be carried out to determine whether there is an unreasonable risk.

(2) Qualitative risk characterization

When PEC or PNEC values for a chemical are not available, qualitative methods can be used to characterize the likelihood of a potential environmental risk occurring. For example:

When the PEC cannot be reasonably estimated, if the qualitative exposure assessment shows that the environmental exposure of the chemical substance will not have a significant impact on any object of assessment, the environmental risk may be ignored; if the qualitative exposure assessment shows that the chemical substance has significant environmental exposure, comprehensive professional judgment is required based on the bioaccumulation potential of the chemical substance and relevant data of other substances with similar structure.

In cases where PNEC cannot be reasonably estimated, where no toxic effects are found in short-term testing and long-term ecotoxicity data are lacking, a qualitative assessment is required to determine whether further long-term toxicity testing is necessary. Qualitative assessment should take into account the level of environmental exposure and the possibility of chronic toxic effects.

2. Health risk characterization

Health risk characterization is a qualitative or quantitative representation of the relationship between a human body's exposure level and a safe threshold or safe dose. For the same chemical substance, different exposure scenarios and exposure populations, different health hazard effects, the risk characterization results are also different.

Characterize the health risks of chemicals by comparing the relationship between total human exposure and safety thresholds (such as TDI) or safe doses:

(1) If the exposure of the chemical substance is less than the safe threshold or safe dose, it indicates that the chemical substance has not been found to present an unreasonable health risk.

(2) If the exposure of the chemical substance is greater than or equal to the safety threshold or safe dose, it indicates that the chemical substance has an unreasonable health risk.

In view of the uncertainty of risk assessment, for the above two situations, according to the specific circumstances, the weight of evidence, expert judgment and other methods can be used to determine whether further exposure and toxicity data need to be collected, and further risk assessment can be carried out to determine whether there is an unreasonable risk.

Qualitative methods can be used to characterize the likelihood of a potential human health risk when a human health safety threshold or safe dose of a chemical is not available.

Preparation of 4. report

The environmental risk assessment report of chemical substances mainly includes: assessment purpose, assessment scope, data collection and data assessment, hazard identification, dose (concentration)-response (effect) assessment, exposure assessment, risk characterization, uncertainty analysis, assessment conclusion, etc.