Hazards and risk assessment of heavy metals from consumption of locally manufactured painkiller drugs in Nigeria

Abstract In the informal sector of Nigeria’s economy, jobs are done manually as against automation resulting in body stress and pain, hence the need for painkiller drugs. Thirty different locally manufactured painkiller drugs, with analgesic, antipyretic and anti-inflammatory effects, were randomly sampled from pharmaceutical shops within Awka in October 2016. The drugs were pulverised, sieved and ashed before digestion using conc aqua regia HCl : HNO3 (3:1), carcinogenic heavy metals (arsenic, cadmium, chromium, mercury, nicked and lead) were assayed using Varian AA240 atomic absorption spectrophotometer (AAS). Risk assessment was carried out using US EPA model. The highest levels of arsenic (0.350 mg/kg) were found in samples with code 01, 03 and 020, cadmium (0.107 mg/kg and 0.144 mg/kg) were in samples code 013 and 028, and samples 03 and 011 had chromium levels as 6.637 mg/kg and 5.298 mg/kg. Highest value of mercury (0.470 mg/kg) was in sample code 01. All the painkiller drugs have nickel in the range of 0.046−0.448 mg/kg while highest values of lead were in sample code 05, 025 and 029 as 2.47 mg/kg, 1.11 mg/kg and 1.16 mg/kg. Non-cancer risk ranged as As (Nd -1.60 × 10−3), Cd (Nd–1.97 × 10−4), Cr (Nd-6.06 × 10−6), Hg (Nd–2.15 × 10−4), Ni (9.93 × 10-6–3.34 × 10−5) and Pb (Nd-4.36 × 10−4) while the cancer risk were As (Nd-1.63 × 10−7), Cd (Nd–4.45 × 10−9), Cr (Nd–1.56 × 10−7), Hg (Nd -1.53 × 10−9), Ni (1.50 × 10−10 –1.46 × 10−9) and Pb (Nd-8.82 × 10−9). The total cancer risk (TCR) and total non-cancer risk (TNCR) for all the heavy metals were in the range of 7.21 × 10−13–1.25 × 10−10 and 1.51 × 10−7–5.56 × 10−5 respectively. The TCR was below 1 × 10−6 -1 × 10−4 range while TNCR for heavy metals was below 1; the values established by US EPA. In conclusion, continuous consumption of locally Nigerian made painkiller drugs may expose the subjects to heavy metal toxicity.