This study aimed to analyze the LC50 value of metallic lead (Pb), chromium (Cr), and cobalt (Co) contained in the printing industry wastewater to Daphnia magna and analyze the relationship of these metals to the LC50 value. The measurement results konsnetrasi Pb and Cr do not exceed the quality standards established, but the metals Co exceeds quality standards. Toxicity of Pb, Cr, and Co were tested in static test using artificial solution of Pb, Cr, and Co in accordance with the concentration measured in the wastewater. Tests carried out consisted of two stages: a preliminary test and test base. Daphnia magna mortality data were analyzed using Probit method with the EPA program Probit Analysis Program Version 1.5. 24-hour LC50 value of Pb, Cr, and Co to Daphnia magna is 1.052% and the LC50 values of Pb, Cr, and Co are respectively 0.003 mg / l, 0.008 mg / l and 0.009 mg / l. All three metals have included the category of very toxic to Dahnia magna.Keywords: Pb, Cr, Co, Daphnia magna, LC50Abstrak-Penelitian ini bertujuan untuk menganalisis nilai LC50 logam timbal (Pb), Krom (Cr), dan Kobalt (Co) yang terdapat pada limbah cair industri percetakan terhadap Daphnia magna serta menganalisis hubungan logam tersebut terhadap nilai LC50. Hasil pengukuran konsnetrasi logam Pb dan Cr tidak melebihi baku mutu yang ditetapkan, namun logam Co melebihi baku mutu. Toksisitas logam Pb, Cr, dan Co diuji dalam static test menggunakan larutan artifisial logam Pb, Cr, dan Co sesuai dengan konsentrasi terukur pada limbah cair. Pengujian dilakukan terdiri dari 2 tahap yaitu uji pendahuluan dan uji dasar. Data kematian Daphnia magna dianalisis menggunakan Metode Probit dengan program EPA Probit Analysis Program Version 1.5. Nilai LC50 24 jam logam Pb, Cr, dan Co terhadap Daphnia magna adalah 1,052% dan nilai LC50 logam Pb, Cr, dan Co berturut-turut adalah 0,003 mg/l, 0,008 mg/l, dan 0,009 mg/l. Ketiga logam ini termasuk kategori sangat toksik terhadap Dahnia magna.Kata Kunci: Pb, Cr, Co, Daphnia magna, LC50
Modeling Bayesian Networks from a conceptual framework for occupational risk analysis