TOXIC OIL SYNDROME

HISTORY

In the early 1980s, Spanish laws banned the importation

of rapeseed oil for human consumption to protect the

Spanish olive oil market. These laws required the

denaturation of imported rapeseed oil with aniline,

methylene blue, or castor oil as a means to make this

imported oil unfi t for human consumption. During late

1980 and early 1981, a substantial amount of aniline -

denatured rapeseed oil imported from France was

fraudulently diverted for human consumption through

Catalonia. These oils were diluted with other edible oils,

refi ned, and resold through a network of distributors

and itinerant salesmen. Although these oils contained

aniline, the toxic oil syndrome was apparently not associated

with the aniline.

During the fi rst quarter of 1981, an oil distributor

based in the center of Madrid named RAELCA entered

the illicit oil sales market with mixed aniline - denatured

rapeseed oil. In March 1981, RAELCA purchased fi ve

lots of aniline - denatured rapeseed oil from two French

food oil companies, and they shipped three lots to the

ITH oil refi nery in Seville. The other two lots went to

the Danesa Bau refi nery in Madrid. Although the denatured

oils were intended for industrial use, roadside

vendors sold the oils as “ olive oil ” to residents over a

2 - month period. Most of the cases of toxic oil syndrome

appeared in the period from May to August 1981.

Figure  displays the number of cases of toxic oil syndrome

diagnosed in 1981. Epidemiological studies concluded

that the ITH oil refi nery was the point source for

the epidemic. 

EXPOSURE

Source

The exact causal agent in the contaminated oil involved

with toxic oil syndrome remains unknown, in part,

because of the many potential toxins in denatured

aniline compounds associated with this illness. In a study

of toxic oil syndrome - associated oils, fractionation of

the oils by high performance liquid with ultraviolet

detection (HPLC/UV) and analysis by high performance

liquid chromatography/atmospheric pressure

chemical ionization/ tandem mass spectrometry (HPLC/

APCI/MS/MS) demonstrated 115 aniline derivatives

from nine aniline - related families of chemicals. Toxic

oil syndrome is a unique combination of vasculitis,

thrombosis, and immunologic changes (e.g., T - lymphocyte

activation, cytokine release) that differs from the

toxicity previously associated with refi nery products,

additives, or contaminants.The full spectrum of toxic

oil syndrome has not been reproduced in experimental

animals. The two suspected groups of toxic compounds

are fatty acid anilides and amino - propanediol derivatives

(fatty acid mono - and di - esters). Analysis of contaminated

oil samples indicates that pentachlorophenol

and pentachloroanisole were not etiological agents of

toxic oil syndrome.

Food Processing

In contrast to other illicit rapeseed oil distributors,

RAELCA mixed the denatured rapeseed oil with other

oils after the refi ning process. All other illicit refi ners of

denatured rapeseed oil in Catalonia mixed the denatured

and edible oils before refi ning the adulterated oils.

The processing of the fraudulently diverted rapeseed oil

probably contributed to the formation of toxic compounds

in the oil. High temperatures during deodorization

catalyzed the reaction of 2% aniline with triglycerides

in the rapeseed oil associated with toxic oil syndrome. 

In experimental studies, the yield of 3 - ( N - phenylamino) -

1,2 - propanediol (PAP) esters in toxic oil syndrome is

highest at 250 – 300 ° C ( ∼ 480–570 ° F), similar to those

temperatures achieved during the deodorizing step of oil

refi ning.  These studies indicate that the heating of denatured

oil samples stored for 3 weeks yields higher concentrations

of potentially toxic PAP esters compared

with samples stored for 1 week. Distillations times did

not signifi cantly affect the formation of fatty acid anilide

compounds. The development of toxic oil syndrome following

the ingestion of denatured rapeseed oil stored for

about 1 year suggests that the toxic compounds in these

contaminated cooking oils are stable for at least 1 year. 

DOSE RESPONSE

Dose response in toxic oil syndrome was evaluated by

a case control study known as the “ Toxi - Epi Study, ”

which followed sales and distribution chains of the

fraudulently distributed rapeseed oils using the chemical

markers, oleyl - anilide and di - oleyl - 3 - phenylamino -

1,2 - propanediol (OOPAP). The content of these

compounds varied several fold in different samples of

contaminated cooking oil. Cooking oil containers with

a characteristic shape purchased by residents were

traced back to the ITH oil refi nery in Seville in southern

Spain. Analytical studies showed a linear statistical correlation

between the concentration of the chemical

markers detected in the refi nery ’ s oil and the log of the

odds ratio for dose - response. 50 Rapeseed oil concentrations

of oleyl - anilide and OOPAP traced to this plant

were 1900 ppm and 150 ppm, respectively.

CLINICAL RESPONSE

The fi rst cases of toxic oil syndrome were reported on

May 1, 1981 in central and northwestern Spain. Initial

epidemiological studies demonstrated clustering in incidence

and mortality for toxic oil syndrome in households

distributed along transportation routes throughout

the affected regions. In July 1981, Spanish health offi -

cials announced that a fraudulently distributed, industrial

oil sold as edible cooking oil was the etiology of

this illness, initially termed pneumonic paralytic eosinophilic

syndrome.The Spanish government subsequently

initiated a consumer exchange program for

olive oil, and they stockpiled the contaminated oil for

further study.In 1983, the World Health Organization

named the illness toxic oil syndrome. The offi cial

census originally consisted of records of patients with

clinically suspected toxic oil syndrome that did not necessarily

fulfi ll the case defi nition of the 1981 Spanish

Clinical Commission. A 1987 review of these records by

the World Health Organization Regional Offi ce for

Europe Scientifi c Committee for the Investigation of

the Toxic Oil Syndrome indicated that about 20,000

people were affected with over 10,000 hospitalizations. 

Although during the fi rst few years about 300 patients

died of toxic oil syndrome, the overall mortality of the

cohort with toxic oil syndrome was not elevated after

the fi rst year of the epidemic when compared with the

general Spanish population.

Toxic oil syndrome is a progressive multisystemic

disease with three distinct clinical phases (acute, intermediate,

chronic). The average latency period was about

4 to 7 days after the ingestion of the contaminated oil

with a maximum of about 10 days. 56 The basic underlying

pathological lesion is a nonnecrotizing vasculitis with

associated thrombotic events. Common initial symptoms

of toxic oil syndrome included fever, cough, dyspnea, and

chest pain. Other acute symptoms included urticarial

rash, pruritus, abdominal cramping, and headache. The

differential diagnosis for toxic oil syndrome includes

other autoimmune disorders such as eosinophilia -

myalgia syndrome, eosinophilic fasciitis, systemic sclerosis,

scleroderma, and systemic lupus erythematosus. 

Porphyria cutanea tarda did not occur in these patients.

Acute (Pulmonary)

The characteristic manifestation of the acute phase is the

development of noncardiogenic pulmonary edema with

dyspnea, alveolar - interstitial infi ltrates with or without

pleural effusions, peripheral eosinophilia, fever, and rash.

Most patients recovered from this early pneumonic

phase of the illness. Deaths during this phase occurred

from respiratory insuffi ciency initially from degeneration

of type I and type II pneumocytes and later from

thromboembolic complications.  During the acute phase

(i.e., fi rst 2 months), the primary lesion occurs in the

endothelium of multiple organs with the exception of the

central nervous system.  Severe myalgias and muscle

cramps occur at the end of the acute phase. 

Intermediate (Thrombotic)

About 60% of the patients with the acute phase progress

to the intermediate phase that involved the development

of sensory peripheral neuropathy along with

intense myalgias, dermal induration, and weight loss.

More serious complications during this phase began

about 2 months after the onset of illness, including pulmonary

hypertension and thromboembolism of large

vessels. In severe cases, histological examination demonstrated

proliferation of the intimal lining of the vessels

along with fi brosis and thrombosis.

Chronic (Neuromuscular)

Approximately 2 months after the onset of the intermediate

phase, the chronic phase of toxic oil syndrome

began, characterized by sclerodermiform changes, motor

neuropathy, musculoskeletal contractures, muscle

wasting, myalgias, muscle cramps, weight loss, limited

joint mobility, peripheral eosinophilia, hepatomegaly,

pulmonary hypertension, and Sj ö gren syndrome. 60 Some

patients developed this chronic phase without experiencing

the acute pneumonic phase.  The most common

persistent symptoms were cough and dyspnea with

about 20% of affected patients developing reduction in

the carbon monoxide diffusing capacity.Mortality in

the chronic phase was primarily due to infectious complications

of respiratory insuffi ciency secondary to neuromuscular

weakness, thromboembolism, or pulmonary

hypertension with cor pulmonale. A minority of toxic

oil syndrome patients developed severe pulmonary

arterial hypertension during exercise over 20 years after

exposure.Long - term follow - up studies of survivors

suggest reduction in the quality of life of these patients

with elevated rates of depression (odds ratio [OR] =

9.66), functional disabilities (OR = 4.74), and psychosocial

disabilities (OR = 2.82). 

Mortality was high during the fi rst year, with a signifi

cant decline in mortality rates in subsequent years.

Most of the decline in mortality was observed in elderly

populations; however, the mortality rate in women < 40

years of age increased as a result of complications from

pulmonary hypertension.Concurrent clustering of

incidence and mortality in toxic oil syndrome suggested

that a genetic predisposition determines the severity of

toxic oil syndrome. Linkage mapping of the human

genome revealed increased mortality in patients with a

chromosome 6 - associated risk factor for the HLA - DR2

phenotype.Studies in enzyme mechanics implicate a

role for impaired hepatic acetylation in mediating individual

susceptibilities to toxic oil syndrome. 

DIAGNOSTIC TESTING

Analytical Methods

Analytical methods to identify and quantify OOPAP

and other PAPs in contaminated cooking oil samples

include high performance liquid chromatography/atmospheric

pressure ionization/tandem mass spectrometry

(HPLC/API/MS/MS) and HPLC/MS. 

Biomarkers

The analysis of contaminated oil was complicated by

poor identifi cation markers on cooking oil bottles during

the recall process. Two case control studies suggested a

dose - related association between the presence of three

fatty acid anilide compounds (oleyl, linoleyl, palmityl)

and the risk of developing toxic oil syndrome. Of

these fatty acid anilide compounds, oleyl anilide occurred

in the highest concentration. Subsequent analyses

suggested that 3 - ( N - phenylamino) - 1,2 - propanediol

(DEPAP), a by - product of the same reaction of aniline

with triglycerides, is an equally sensitive and a more

specifi c biomarker of toxic oil syndrome than fatty

anilide compounds. 71 Animal studies suggest that the

liver converts fatty acid mono - and diesters of 3 - ( N -

phenylamino)propane - 1,2 - diol to 3 - (4 ′ - hydroxyphenylamino)

- propane - 1,2 - diol, which generates the

electrophilic metabolite quinoneimine intermediate - 2

(QI - 2). However, the specifi c chemical causing toxic

oil syndrome has not been identifi ed.

Abnormalities

Laboratory changes associated with toxic oil syndrome

include peripheral eosinophilia, hypertriglyceridemia,

and coagulation disorders in patients with liver involvement.

Analytical studies of toxic oil syndrome patients

demonstrate eosinophilia and a high concentration of

mRNA for T - helper - 2 cytokines, IL - 4 and IL - 5, in the

lungs. Antemortem sera from fatal cases of toxic oil

syndrome also contained elevated serum IL - 2R and

total IgE concentrations along with a high frequency of

HLA - DR2 on chromosome 6. The sinus and atrioventricular

nodes may exhibit dense fi brosis, hemorrhages,

or cystic degeneration similar to fi ndings in scleroderma

and systemic lupus erythematosus. Coronary arteries

may exhibit focal fi bromuscular dysplasia and cystic

myointimal degeneration with embolization. Histopathological

analyses show lymphocytic infl ammatory lesions

of coronary arteries and the cardiac conduction system,

similar to the fi ndings in eosinophilia - myalgia syndrome.

Cardiac lesions associated with eosinophilia - myalgia

syndrome, however, are distinguished by cytotoxic T -

cells directed against cardiac neural structures and sinus

nodal myocytes, whereas toxic oil syndrome cardiac

lesions are characterized by a prominence of B cells and

T - helper cells.

Chest x - ray demonstrates an interstitial - alveolar

pattern with progression to acute respiratory distress

syndrome (adult respiratory distress syndrome or

ARDS) in the acute phase of toxic oil syndrome. Eosinophilia

is a universal fi nding in toxic oil syndrome

patients. Hypoxemia, respiratory alkalosis, and an

increased alveolar - arterial oxygen gradient (A - a gradient)

as determined by arterial blood gases are common

in patients with severe toxic oil syndrome - induced noncardiogenic

pulmonary edema during the acute phase. 

TREATMENT

During the acute phase, respiratory compromise from

ARDS is the most serious complications of toxic oil

syndrome. Patients with toxic oil syndrome are also at

increased risk of cardiovascular disease that may manifest

several years after exposure. Echocardiography,

cholesterol screening, and weight management are effective

tools for the screening and detection of cardiovascular

sequelae in patients with toxic oil syndrome. 

Long - term neuromuscular and articular complaints are

prominent, and abnormalities are treated symptomatically.

 Patients should be monitored for the prominent

risk factors most closely associated with early mortality:

female < 40 years old, liver disease, pulmonary hypertension,

frequent pulmonary infections, motor neuropathy,

and eosinophilia.