# Presentation: 297656

## Pesticides in urban settings – Use of a Pesticide Toxicity Index to evaluate potential toxicity of stream water samples to macroinvertebrates

- by
- Karen Riva-Murray, Patrick J. Phillips,
- Robert W. Bode, and Mark D. Munn

##  Commonly applied in urban settings

-  Commonly applied in urban settings

- What we know about modern-day pesticides:

-  Have a wide range of toxicities to aquatic organisms

-  Large spatial and temporal variation

-  Tend to occur as complex mixtures

-  Detected in stream water

**Notes:**
In fact, Pat Phillips has just shown you how oncentrations, p[articularly of inse cticides, increase with increasing urbanization in the Croton wastershed.

##  Factors affecting potential toxicity

-  Factors affecting potential toxicity

- What we ^ know:

- don’t

-  Combined toxicity of the entire pesticide mixture

-  Response of stream biota

**Notes:**
As with many other nonpoint issues, it is more challenging to link stream water pesticide concentrations to effects on aquatic biota.

## Pesticide Toxicity Index (PTI)

- Munn, M.D. and Gilliom, R.J., 2001, Pesticide Toxicity Index for freshwater aquatic organisms: U.S. Geological Survey Water-Resources Investigations Report 01-4077, 61 p.

**Notes:**
Integrates measured exposure (stream concentrations) with biological effects (bioassays)

## Objectives:

- How does PTI vary in relation to urbanization?

- What other factors influence PTI in urban settings?

- Does change in PTI correspond with change in  biological indicators?

**Notes:**
Land use, hydrologic factors, application practices, regulations

## PTI Cautions and Caveats :

- Pesticides may not be included in lab analyses

- Use for relative rankings - not actual ‘toxicity’

- Bioassays done on limited taxa

- Toxicities not available for all pesticides

- Synergistic effects not accounted for

## Study Area – 

- Study Area –

- Croton watershed
- NYC water supply
- 47 sites
- small streams
- range of urban

**Notes:**
watershed of major NYC water supply reservoir 
 Sites have a range of developed land, mostly urban 
 47 sites sampled in 2000 – base-flow, late summer
 Kisco River -- sampled multiple times 2000-2003
 2-4 times per month
 & storms 

## Methods-

- Water samples:
- All sites: Base-flow
- summer 2000
- Kisco R. site: 2-4X/month
- & storms 2000-03

- Macroinvertebrates:
- Baseflow
- summer 2000

## Results – Bioassessment index versus urban intensity

## Results – PTI versus urban intensity indicator

- PTI score + 10-8

- .00000001

## Results – Similar to other urban areas

- Source – NAWQA summary reports

## Results – Bioassessment versus PTI score

**Notes:**
Open diamonds represent sites affected by poor habitat, upstream dams, and other factors

## Results – Temporal variation; Kisco R. May 01-Sept 03

## Results – PTI does not track total concentration

**Notes:**
Pesticide data from Kisco R May-Sept each year.

## Conclusions: 

- Conclusions:

- More information is needed
- 	- Toxicities of newer pesticides
-  	- Long-term trends in toxicity
- 	- Synergistic effects

- Relative PTI likely to increase with further urbanization

- Pesticide toxicity may be an important contributing factor to decline in aquatic biological health in urban streams