Two Cases of Methemoglobinemia Induced by the Exposure to Nitrobenzene and Aniline

Abstract

ObjectiveTo report two cases of methemoglobinemia induced by inhaled nitrobenzene and dermally absorbed aniline.MethodsWe have evaluated a 37-year-old male worker exposed to nitrobenzene by inhalation while conducting maintenance job of mononitrobenzene pump and a 25-year-old male worker exposed dermally to aniline while unloading.ResultsThe first case is a 37-year-old male exposed to nitrobenzene. His blood methemoglobin concentration level was initially 19.8%, and chest X-ray was normal. After oxygen therapy, the blood methemoglobin concentration level decreased to 2.1%, and the symptoms were alleviated. The second case is a 25-year-old male exposed dermally to aniline. His chest X-ray was normal, but blood methemoglobin concentration level reached maximally 46.8%. He was treated with methylene blue due to relatively high blood methemoglobin level. Gradually after the treatment, his methemoglobin concentration level was normalized to 0.8% and simultaneously symptoms were resolved.ConclusionsAfter the thorough exposure investigations and medical evaluations, we have concluded that these cases were methemoglobinemia induced by occupational exposure to nitrobenzene and aniline. We suggest that businesses which handle methemoglobinemia-causing substances control the engineering process strictly, implement periodic screening, and establish emergency patient management system.

The painted shoes

“…The exposure to these compounds may occur via oral ingestion and absorption through the lungs or skin, and may result in clinically significant methaemoglobinaemia, depending on the concentration of MetHb in the blood 4 5. In our case, there were dye stains inside the patient's shoes, and on his socks and feet, suggesting cutaneous absorption.…”

“…In normal circumstances, MetHb levels are less than 1%,5 due to endogenous mechanisms that protect against oxidative stress. Nevertheless, the exposure to an oxidising agent, such as aniline, or to its metabolites, increases the conversion of Hb to MetHb, which may overwhelm these protective mechanisms 2 6…”

Peri operative Management of a Patient with Methaemoglobinaemia Posted for Caesarean Section

“…Methaemoglobin is an oxygenation product of haemoglobin (Hb) where ferrous ion is oxidized to ferric form which is incapable of carrying oxygen [7]. Normally small amount of Hb is continuously being oxidized by endogenous agents.…”

A 48–year–old female presented with severe neck pain

“…12 In industry, workers may develop methemoglobinemia when exposed to commonly used industrial agents such as nitrobenzene, trinitrobenzine and aniline which usually absorb through the respiratory tract or skin. 13 Household chemicals such as furniture and shoe polish containing nitrobenzene, marking ink, shoe dyes, colored crayons containing aniline, perfumes and flavoring essence are also capable of producing methemoglobinemia. 14 Hereditary methemoglobinemia occurs due to deficiency of NADH cytochrome b5 reductase in the red cells causing increased blood level of methemoglobin reducing oxygen-carrying capacity of blood.…”