Magnesium hydroxide

Endpoint summary

Description of key information

Single cases of magnesium poisoning after medical applications of very high dose levels and exposure routes not relevant for the industrial uses of Magnesium hydroxide were reported in the literature.

Additional information

An inhalation study on human exposure to Magnesium oxide particles was carried out, with the goal of the study to characterize human pulmonary responses to controlled experimental high-dose exposure to fine and ultrafine Magnesium oxide particles. In conclusion, Magnesium oxide did not show any toxicity towards the six subjects tested. Therefore, there were no adverse effects noted in humans exposed to Magnesium oxide particles by inhalation.

A few studies are reported in the literature were administration of magnesium hydroxide directly into the gut led to fatal outcomes. A report where a girl with a long history of constipation was accidentally administered half a Fletchers Magnesium sulphate enema, concludes that Magnesium poisoning can occur if exposed to large amounts of Magnesium sulphate but as the child was chronically constipated and a chronically dilated rectum and colon probably provided a greater surface area for the absorption. Therefore, this is an unusual case. In another five similar cases, the death of each patient occurred after the introduction into the duodenum of Magnesium sulphate solution, even if atebrine was administered first there was no change, the clinical symptoms of poisoning appeared immediately after the introduction of Magnesium sulphate.

Side effects mostly of transient nature on the fetus during therapeutic use of magnesium sulphate intravenous infusions as tocolytic agent (mostly in combination with other medicines) in the management of preterm labour have been reported at dose levels that exceeded the therapeutic doses. The majority of the studies did not observe any adverse effects on the newborns.  Babaknia et al, 1978 reported two cases a reversible reduced variability of fetal heart rate during infusions of magnesium sulphate to pregnant women suffering from hypertension and also receiving other medical drugs. Peaceman et al, 1989 studied effects on fetal stress reactions of magnesium sulphate infusions to 16 pregnant women (6 pregnant with twins) with preterm labour. The authors report a decrease in fetal heart rate in 16 of 22 fetuses and a reduction in fetal breathing movements in 18 of 22 fetuses while all fetuses revealed normal tone and gross movements and amniotic fluid volumes. No effects on the newborn after delivery were reported. The fact that newborns are not adversely affected by treatment of mothers with tocolytic doses of magnesium sulphate was corroborated by an epidemiological study of Schendel et al., 1996 who examined the risk of cerebral palsy or mental retardation in a cohort of very low birthweight children whose mothers were treated with magnesium sulphate during pregnancy. The children were followed up to one year of age including a subcohort followed up until 3 to 5 years of age. The study included all very low birth weight infants born during a 2-year period inand 24 counties in. The authors report a 90% lower prevalence of cerebral palsy and a 70% lower prevalence of mental retardation in children whose mothers were treated with magnesium sulphate during pregnancy compared to the chohort that did not receive magnesium sulphate. Herschel and Mittendorf, 2001 report one case of a women pregnant with twins that received magnesium sulphate infusions, antibiotics and betametasone following a spontaneous rupture of the membranes and contractions. The women received an overdose of magnesium sulphate with Mg²⁺blood levels of 9 mg/dl. After cessation of the infusion and a caesarian delivery one of the twin infants died. The authors report that this was probably related to the magnesium sulphate overdose, but a clear causal relationship cannot be deduced from this case report. Intravenously administered sulphate was reported to be well tolerated and beneficial in the treatment of eclampsia for both mother and infant at therapeutic magnesium serum concentrations of about 2 to 3.5 mmol/L (Lu, J. F. and Nightingale, C. H., 2000). Magnesium sulphate administered by deep intramuscular injection at does levels of 30 to 40g per day to pregnant women that were monitored for the absence of effects on the knee jerc reflex, urine flow and respiratory rate, was reported to have no  effects on the neonatal mortality rate (Stone et al, 1970)In addition to this, human health questionnaires were distributed among eight magnesium hydroxide producing companies where, overall, 457 workers are exposed to Magnesium hydroxide,182 of those are exposed continuously and 227 are exposed intermittently. These workers were questioned on any adverse effects or health problems they may have experienced due to exposure; these included skin allergy or occupational asthma. Among all the workers surveyed, there were no reported cases, from any of the 457 workers, of health problems or adverse effects experienced through exposure. (ref)

In conclusion, according to the human health questionnaires distributed through 8 different companies where 457 total workers are exposed to Magnesium hydroxide on a regular basis, no exposure related health problems including skin allergy or occupational asthma, were reported. There were also no adverse effects reported from the workers during each operation, even in cases where PPE was not used for some of the procedures in some companies.