the water quality monitoring results in Tables 5.55 and 5.56, nitrate, nitrite and
manganese covered by the drinking water standards exceed the limits and remediation can be conducted directly. Chloride, ammonia nitrogen, and fluoride which
are not covered by such standards are also detected, which necessitates groundwater
health risk assessment.
The screening levels for chloride, ammonia nitrogen, and fluoride are calculated
using the HERA model.
The monitoring results indicated in Tables 5.55 and 5.56 are compared with the
screening levels shown in Table 5.59. Both chlorine and fluorine exceed the
screening levels. There is no risk of exposure to ammonia nitrogen because the
exposure pathway is not included in this assessment. Given this, chlorine and
fluorine are identified as the focus pollutants of health risk assessment of groundwater environment.
(b) Toxicity assessment
Based on the results of hazard identification, toxicity assessment is conducted for
focus pollutants.
• Carcinogenicity identification
The carcinogenicity of focus pollutants is identified according to the findings of
IARC and IRIS. The IARC system for carcinogenicity classification is preferred,
followed by the US EPA system. As shown in Table 5.60, the two focus pollutants
are found carcinogenic.
• Toxicity values
China mainly uses the relevant US evaluation system, and its values are all obtained
from the aforementioned US toxicological databases. Each contaminant toxicological concern parameters in Table 5.61.
The relevant US assessment systems are adopted, wherein the toxicity values are
all obtained from the aforementioned databases. The toxicity values of focus pollutants are as shown in Table 5.61.
(c) Exposure assessment
Exposure assessment is a process of measuring, estimating or predicting the
magnitude, frequency and duration of human exposure to pollutants in the media,
which serves as a quantitative basis for risk assessment. It includes the assessment
of the scenarios, media, pathways, concentrations, and quantities of exposure.
• Types of land use
According to the hydrogeological conditions of the landfill, there are 83 households
from Fengle Village 194–691 m from the landfill, and all of them draw groundwater through wells (manually operated steel pipe wells) for production and
domestic use. It is determined that the pollution plume of the landfill covers
groundwater-based drinking water sources, and pose potential health hazards to
surrounding off-site receptors. Therefore, in this health risk assessment, the in situ
5.3 Southwest China
205
manganese covered by the drinking water standards exceed the limits and remediation can be conducted directly. Chloride, ammonia nitrogen, and fluoride which
are not covered by such standards are also detected, which necessitates groundwater
health risk assessment.
The screening levels for chloride, ammonia nitrogen, and fluoride are calculated
using the HERA model.
The monitoring results indicated in Tables 5.55 and 5.56 are compared with the
screening levels shown in Table 5.59. Both chlorine and fluorine exceed the
screening levels. There is no risk of exposure to ammonia nitrogen because the
exposure pathway is not included in this assessment. Given this, chlorine and
fluorine are identified as the focus pollutants of health risk assessment of groundwater environment.
(b) Toxicity assessment
Based on the results of hazard identification, toxicity assessment is conducted for
focus pollutants.
• Carcinogenicity identification
The carcinogenicity of focus pollutants is identified according to the findings of
IARC and IRIS. The IARC system for carcinogenicity classification is preferred,
followed by the US EPA system. As shown in Table 5.60, the two focus pollutants
are found carcinogenic.
• Toxicity values
China mainly uses the relevant US evaluation system, and its values are all obtained
from the aforementioned US toxicological databases. Each contaminant toxicological concern parameters in Table 5.61.
The relevant US assessment systems are adopted, wherein the toxicity values are
all obtained from the aforementioned databases. The toxicity values of focus pollutants are as shown in Table 5.61.
(c) Exposure assessment
Exposure assessment is a process of measuring, estimating or predicting the
magnitude, frequency and duration of human exposure to pollutants in the media,
which serves as a quantitative basis for risk assessment. It includes the assessment
of the scenarios, media, pathways, concentrations, and quantities of exposure.
• Types of land use
According to the hydrogeological conditions of the landfill, there are 83 households
from Fengle Village 194–691 m from the landfill, and all of them draw groundwater through wells (manually operated steel pipe wells) for production and
domestic use. It is determined that the pollution plume of the landfill covers
groundwater-based drinking water sources, and pose potential health hazards to
surrounding off-site receptors. Therefore, in this health risk assessment, the in situ
5.3 Southwest China
205