Formaldehyde

To determine the neurobehavioral effects of formaldehyde exposure in 22 subjects and whether patterns of effect differed in 3 groups: 5 patients with 11-24 month exposures to phenol-HCHO resin fiberglass fabrication of airliner parts, 6 exposed to carbonless copy paper (CCP) and 8 exposed in anatomy, pathology or dentistry laboratories (2 were truckers and 1 a carpenter). Test scores were compared individually and collectively to combined population based predicted values based on 4 samples of unexposed people in the USA.

The dental technician and the pathologist had probably been exposed briefly to high levels of formaldehyde, as well as low levels. The pathologist had daily occupational exposure for 20 years, after some exposure as a medical student and as post doctoral trainee in pathology. Several days of intensive exposure to formaldehyde occurred during cleaning-up his laboratory without ventilation after an earthquake. Testing showed a prolonged reaction time and abnormal balance with eyes closed that he had noted as motion sickness and clumsiness while walking. Testing at six months interval that began several months after his exposure showed gradual worsening of reaction time and balance with eyes closed, prolongation of blink reflex and arcuate scotomas grew into superior quadrant defects in the visual fields of both eyes. Also his cognitive functions, problem solving, dropped from superior levels to average particularly in block design and digit symbol while the verbal story recall score was halved across the interval of follow-up and trail making slowed from normal to three times normal values. Mood state score increased with elevated anger, confusion, tension and fatigue scores. Concern about his probability of making diagnostic errors made him retire from pathology.

Other patients with formaldehyde exposure had neurobehavioral impairment. Most of them had worked in anatomy laboratories or had prepared specimens for anatomy, one was a medical student taking human anatomy, one was a pathologist, one was a construction worker and one made a delivery to a chemical plant venting formaldehyde. Six used carbonless copy paper and five others formed parts from phenolformaldehyde fiberglass resins for aircraft cabins. All had had the irritative acute symptoms. Only the student made a complete recovery. The others developed both airway and brain impairment. Phenol and methanol, both components of formalin used in the laboratory may contribute to ill effects on the brain although phenol becomes poorly gaseous to a high vapor pressure. Ingestion of methanol, however, is a known cause of blindness and it is a major metabolic product of formaldehyde. They share the toxicity of formic acid. However, the avid cross linking of formaldehyde with proteins as with phenols to make resins have suggested that neurofilaments vital for nerve cell nutrition are destroyed (cross linked) on the long processes (axons) in the brain to kill these neurons. This plausible idea should be verified or a better explanation found. The patients join those described earlier with adverse effects from workplace exposure. As indoor air effects may be due to formaldehyde, exposure should be prevented.

We measured balance by head tracking, simple and two-choice visual reaction time, blink reflex, H-reflex, visual fields, color discrimination and hearing. We tested Culture Fair, digit symbol, vocabulary, slotted pegboard, trail making A and B, finger writing (errors), remote memory and immediate and delayed verbal recall and profiled moods. Comparisons were made as percent predicted to unexposed subjects which adjusted for age, height, school grades completed and other factors. Questionnaires explored chemical exposures, medical, neurologic and psychiatric disease and symptom frequencies for respiratory, muscle and joints, heart and limbic (memory). Spirometry measured pulmonary volumes and flows. A p of <0.05 established statistically significant difference.

Major test abnormalities for balance, choice reaction time and visual field performance were accompanied by decreased grip strength, Culture Fair, digit symbol (cognitive domain), verbal recall, peg placement and trail making A and B. The decrease in forced vital capacities was significant and that for FEV1 nearly so. POMS scores were elevated as were symptom frequencies. Exposure durations varied from a minutes for 2 health workers and a trucker to 30 years. No confounding factors were found. Several patients tested repeatedly showed deterioration greatly in excess of the effects of aging. Impairments were similar in the three exposure groups.

Formaldehyde adversely affected the human central nervous system after long or short-term exposures. A massive episode could trigger symptoms and impair function. CNS impairment appeared to be progressive and irreversible in phenol-HCHO resin fabricators, in CCP exposed and in health workers. Formaldehyde is neurotoxic.