A water channel carrying some of the contaminated water. I groundWork
A water channel carrying some of the contaminated water. I groundWork

Arsenic, pesticides found in beach sediments after Durban factory fire

By Thobeka Ngema Time of article published Sep 15, 2021

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DURBAN - ARSENIC was found in beach sediments and seawater.

Other pesticides were also detected at a “concentration of interest” in the beach sediment and seawater samples.

Samples were taken at the estuary and marine sites. A cocktail of 1 600 chemicals flowed into the uMhlanga tributary, uMhlanga estuary and on to the beach, discolouring the water and killing aquatic life while firefighters battled the blaze at the United Phosphorus Limited (UPL) warehouse in Cornubia, north of Durban, in the July unrest.

Element Materials Technology (EMT) had received 59 samples for analysis on August 9.

Samples were taken at the estuary and marine sites.

Griffon Poison Information Centre director Dr Gerhard Verdoorn said he received the consolidated analytical report from EMT on August 20.

Results of the analysis conducted on sediments and of marine and freshwater were collected on July 28.

Verdoorn said in his personal opinion, the monosodium methyl arsenate (MSMA) at the date of sampling posed no acute risk to people and most probably no chronic risk either.

“If the MSMA is reduced to elemental arsenic, chronic exposure to a daily intake of between 0.05 and 0.5mg/kg body mass may result in serious health effects such as liver cancer.

“The conditions during the fire and in the environment into which MSMA was deposited are not conducive to total reduction of MSMA to elemental arsenic. The significant difference in sediment and seawater concentration of the MSMA indicates very strongly that MSMA is still intact and has not reduced to elemental arsenic,” Verdoorn said.

He said apart from arsenic that was found in both beach sediments and seawater, the only pesticides that were detected at any concentration of interest in the beach sediment and seawater samples were atrazine, diuron and chlorpyrifos.

Verdoorn said it confirmed his opinion that the pesticides that entered the sea via the estuary mouth underwent significant dilution due to dissipation to a point of no concern for human exposure at the date of sampling. None of the substances will singularly pose a risk to human health because of the insignificant concentrations which are all well below the acceptable daily intakes of each individual substance.

Diuron and chlorpyrifos that were detected and quantified pose a risk to marine invertebrates.

He said he could not make any assumptions about the reduction in the pesticide “load” in the sediments and water of the other sample site.

Some substances reflect in low to extremely high concentrations in the sediments:

Dimethoate was detected at a low concentration of 3.8 ug/kg (0.0038 mg/kg at SS2A).

Bromoxynil, clopyralid, ioxynil, picloram, ametryn and atrazine were detected but declined in concentration downstream from the warehouse site.

Terbuthylazine and other triazine herbicides declined in concentration downstream from the warehouse site.

Diuron was detected at 243mg/kg (0.243gram per kg) in the sample sites closest to the warehouse site, which meant a direct deposit of the substance from the warehouse to the tributary.

Insecticides and herbicides detected in the surface waters were chlorpyrifosethyl (insecticide) at 0.157mg/l, dichlorvos (dichlorvos) at 0.0898mg/l, clopyralid (herbicide) at 0.071mg/l, atrazine (herbicide) at 12.596 mg/l and diuron (herbicide) at 4.977mg/l.

“MSMA in the watercourses at the time in samples showed concentrations (retro-calculated from arsenic concentrations) ranging from 2.45mg/k to 443mg/kg in sediments and lower concentrations in the surface waters ranging from 2.205mg/l to 32.34mg/l.

“This is still of human health and environmental health concerns,” said Verdoorn.

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