Six total release chlorpyrifos foggers were used by residents of a wood frame residence in Fresno, CA in June 1997. A situational (opportunistic) urine biomonitoring of the family of four including two children aged 6 and 8 years-of-age produced remarkably greater TCPy equivalents excreted in urine than in previous studies. No adverse effects or signs of toxicity were reported or revealed during follow-up medical examination. Prefogging urine specimens from each family member 5 times during a 4 week period contained 0.06 to 1.6 μg equivalents chlorpyrifos/kg-day based upon 3,4,5-trichloro-2-pyridinol (TCPy; uncorrected). The residence was fogged on 6/28 and the family left for the day (Saturday). Morning urine specimens were provided the next 4 days.
Elevated TCPy levels were seen in each family member within one day. The father excreted 3-times more than his wife (2.0 to 30 μg eq./kg-d). The children excreted more than 20 times more than their mother, who resided indoors for the same time as the children. The 8-year-old excreted 32, 142, 158, and 262 μg eq./kg-d on days the 4 successive mornings after fogging. The children were extremely active and their play was restricted to indoor activities due to extreme heat most of the day. Indoor surfaces that included wood, tile, and berber carpet were also thought to have contributed to greater exposure than nylon carpeting present in all previous homes where our fogging research had been conducted.
Subsequent studies using an ACE Indoor Fogger (EPA Reg. No. 9688-63, contains 0.50% chlorpyrifos) that was discharged following label instructions in a 6 m × 4.7 m × 2.5 m room. The fogger was placed in the middle of the room. The total chlorpyrifos applied in this room was 0.84 gram. Five types of floor covering including nylon carpet, berber carpet, linoleum, tile and wood were laid out as a circle with a radius of 1.2 m. Foil coupons were placed at 0.4, 1.2 and 2.1 m from the fogger. Transferable residues for each flooring were measured after 2, 24, 48 and 192 h using an Automated Surface Wipe (ASW). (ASW is a new transferable residue measurement developed by PCEP). Flooring coupons were simultaneously collected for total surface residue measurement. California roller measurements of transferable residue were used for nylon and berber carpet. More chlorpyrifos was deposited close to the fogger as observed in other studies.
The transferability of surface chlorpyrifos residues over the total study period was as follows: tile ≈ wood > linoleum > nylon carpet ≈ berber carpet. The transferability of chlorpyrifos residues from other flooring in addition to nylon and the intensity of children’s indoor activity at Fresno likely contributed to their excessive absorption and excretion of chlorpyrifos equivalents in this unusual 1997 study.
The results of the chlorpyrifos monitoring were reported to the USEPA and to Dow Agro Sciences as an Adverse Effects Report FIFRA 6(a) (2) in August 1997 and remained unexplained until similar findings were made in support of recent pyrethroid monitoring (Keenan and Krieger, in manuscript).