What is the epidemiology of oxalic acid poisoning?

Epidemiology of Oxalic Acid Poisoning

Geographic Distribution and Emerging Patterns

Oxalic acid poisoning has emerged as a significant public health epidemic in rural Sri Lanka, where it is a component of locally produced household laundry detergents, with a case fatality ratio of 25.4% when oxalic acid alone is ingested. 1, 2

Sri Lankan Epidemic

• Between 2009 and 2012, oxalic acid poisoning became a popular method of self-harm among youth in Southern Sri Lanka, with 115 documented cases in a prospective observational study 2
• The poisoning agent consists of sachets containing 12.5 g of oxalic acid (often combined with 1.2 g of potassium permanganate) sold as laundry detergent 2
• The majority of deaths (most occurring within one hour of ingestion) highlight the rapid lethality of this poisoning, making medical intervention extremely challenging 2
• Ingestion of more than one sachet significantly increases mortality risk (risk ratio = 13.26,95% CI = 3.2-54) 2

Global Context

• In Western populations, oxalic acid exposure is primarily chronic rather than acute, related to dietary intake (mean daily intake 70-150 mg) or endogenous overproduction in primary hyperoxaluria 3, 4
• Acute oxalic acid poisoning outside of Sri Lanka is rare and typically involves accidental or suicidal ingestion of industrial cleaning products 1, 5
• Historical data from 1967 documented suicide attempts using oxalic acid or ethylene glycol (which metabolizes to oxalic acid), though this was uncommon even then 5

Clinical Characteristics and Outcomes

Mortality Patterns

• The case fatality ratio for pure oxalic acid ingestion is 25.4% (95% CI = 14-39%), while combined potassium permanganate and oxalic acid ingestion has a lower fatality ratio of 9.8% (95% CI = 3.2-21%) 2
• Most deaths occur within the first hour post-ingestion, before patients can reach medical care, making this one of the most rapidly fatal poisoning agents 2
• Less than 1% of all poisonings in the United States are fatal, but oxalic acid represents a notable exception to this general pattern when ingested in toxic quantities 6

Clinical Presentation

• The majority of patients develop gastrointestinal symptoms within the first 24 hours, including mucosal ulceration documented on postmortem examination 2
• Acute renal failure is a common complication, with patients developing significant metabolic acidosis requiring hemodialysis 1
• Renal biopsy findings include acute tubulointerstitial nephritis with diffuse moderate acute tubular damage and refractile crystals (calcium oxalate) in tubules 1
• Plasma biochemistry shows elevated oxalic acid levels associated with reduced total and ultrafilterable calcium levels due to calcium oxalate deposition in soft tissues 5

Risk Factors and Demographics

Population at Risk

• Young adults in rural Sri Lankan communities are the primary demographic affected by this emerging epidemic 2
• The product's lack of regulation and easy availability in these communities facilitates its use for self-harm 2
• Vegetarians consuming high-oxalate diets (spinach, rhubarb, beet) have increased chronic exposure but rarely develop acute toxicity 3

Regulatory Context

• This case series highlights a fatal mode of self-poisoning that could be controlled through regulation of the manufacture and sale of oxalic acid-containing products 2
• The compound is not currently regulated in Sri Lanka despite its high lethality 2
• In Western countries, oxalic acid in concentrated forms is typically restricted to industrial use 1

Common Pitfalls in Recognition

• Oxalic acid poisoning may be missed in initial assessment if the specific agent is not identified, as symptoms can mimic other caustic ingestions 1
• The rapid progression to death (within one hour) means that even prompt medical attention may be insufficient for severe ingestions 2
• Calcium oxalate crystal deposition occurs in two forms: crystalline calcium oxalate dihydrate in kidneys and non-crystalline calcium oxalate-lipid complexes in liver and other tissues, which may not be immediately apparent on standard imaging 5