While I agree with you on being responsible, I would like to think that any blood received during a donation is put through a very thorough screening process to identify any issues and if any issues are present then that blood is discarded. Again, I would like to think this is the case in western medicine.
Keep thinking that but you're wrong. Here's the "extensive" tests. note that their is no chemical analysis for toxic or birth defect causing substances.
Blood donations are tested for the following:
ABO and Rh blood types.
Unexpected red blood cell antibodies that are a result of prior transfusion, pregnancy, or other factors.
Hepatitis B surface antigen, indicating a current infection (hepatitis) or carrier state for hepatitis B virus.
Antibody to hepatitis B core antigen, indicator of a present or past infection with the hepatitis B virus.
Antibody to hepatitis C virus, indicating a current or past infection with hepatitis C virus (most common cause of non-A/non-B hepatitis).
Antibody to HTLV-I/II, indicator of infection with a virus that may cause adult T-cell leukemia or neurological disease.
Antibody to HIV-1/2, indicator of infection with human immunodeficiency virus (HIV).
Nucleic Acid Test (NAT) for hepatitis C (HCV), hepatitis B (HBV) and HIV.
Screening test for antibodies to syphilis.
NAT for West Nile Virus (WNV).
Enzyme-linked immunoassay (ELISA) test for Trypanosoma cruzi (Chagas Disease).
In addition, all platelet apheresis donations are tested for bacterial contamination.
http://www.redcrossblood.org/donating-blood/donation-faqs