Biomarkers are biological signals that indicate the harmful effects of pollutants, and can measure the exposure and effects of environmental pollutants. Commonly used biomarkers include parent compounds, phthalate monoesters and secondary metabolites.

a) Urine

Due to its special physiological role, urine often shows greater fluctuations between different individuals and at different stages of the same individual. Large fluctuations under normal conditions precisely explain the sensitivity of urine, which can reflect many physiological changes in the body.

b) Blood

Blood, for a long time, has been considered the main target of biomarker research. A great deal of manpower and material resources have also been invested in this field.

c) Saliva

Saliva is a complex mixture that not only contains various proteins, but also DNA, RNA, fatty acids and various microorganisms, etc. Studies have found that various protein components in the blood are also present in saliva, and saliva can reflect changes in the levels of various proteins in the blood. Therefore, it is possible to diagnose the disease through the detection of saliva.

d) Exhaled condensate

The exhaled breath condensate contains a large number of volatile and non-volatile substances. The changes of these substances can reflect the changes in the respiratory tract environment such as oxidative damage and inflammatory reactions, which can be used to detect changes in diseases. It can be used for early diagnosis and large-scale screening of clinical diseases, and it can also be used for diagnosis of diseases in severely ill patients.

e) Hair

Due to the advantages of non-invasive sampling, time traceability and simple storage, hair has unique advantages in long-term disease monitoring, pathogenesis research and disease process research. At present, the mechanism of the substance curing to the hair is not very clear. The existing research reports mainly include the following ways and methods of curing: 

(1) When the hair is formed, blood-derived substances enter the hair from the capillaries;

(2) After the hair is formed, substances enter the hair follicle from sweat glands and cortical glands; 

(3) Some compounds synthesized by the hair follicle itself. Hair absorbs nutrients from the peripheral blood and grows is considered to be the main mechanism. Metabolites enter the hair follicle from the capillaries and become the hair shaft. Its growth is closely related to the body's metabolism. Abnormal levels of metabolites in the hair are closely related to many diseases. Such as chronic stress disease, neonatal disease and cancer.